Larcan MX1000UX 1000 Watt UHF Translator User Manual mx1ku

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Publication TSM 20-319
TECHNICAL MANUAL
1KW UHF INTERNALLY D IPLEXED TV TRANSMITTER
MX1000U SERIES
LARCAN INC.
228 AMBASSADOR DRIVE
MISSISSAUGA, ONTARIO
CANADA L5T 2J2
PHONE:
FAX:
(905) 564-9222
(905) 564-9244
Rev 1: March 2003
INTRODUCTION
This manual describes the LARCAN model MX1000U, internally diplexed UHF television
transmitter.
LARCAN all-solid-state 1 kW UHF transmitters are designed to operate conservatively at 1 kW
peak sync visual/vision RF power and 100W average aural/sound single carrier RF power, with
superb performance, reliability and operating economy. The MX1000U transmitter accepts an
on-channel internally diplexed (in a 10:1 ratio vis to aur/snd) composite driving signal of 10 mW
peak visual RF, as input to its RF chain.
The 1 kW transmitter is self-contained within a single 19" cabinet with an integral cooling fan and
filtered rear door air intake. The simplicity of design, the employment of modular subassemblies,
and the use of standard readily available components, also enhances serviceability.
Important transmitter parameters are monitored, and can be displayed on the meters built into the
transmitter control panel. Additionally, telemetry readings are made available as DC signals for
monitoring by remote control systems. The MX1000U, like all other LARCAN transmitting
equipment, is suitable for unattended remote-control operation.
AMPLIFIER CHAIN (R EFER TO FIGURE 1)
The Aural signal of the transmitter is diplexed (at IF) with the visual/vision signal within the exciter
(hence the term "internally diplexed), and is amplified in common with the visual signal in the
above amplifier chain (hence the term common amplification).
The internally diplexed composite RF output of the exciter/translator is fed to a 4-way active
splitter. The 4 outputs of the splitter are fed to conservatively designed broadband solid-state
amplifiers. The outputs from the four PA modules are combined for the total transmitter output
power. These amplifiers require no tuning or adjustment. Phasing for the four PA modules is
done at the splitter level. Internal cable lengths and precise production tolerances allow for a very
small adjustment range for phasing. Simplicity of operation, reduced maintenance costs and
increased reliability are a few of the major benefits derived from this modular amplifier design.
The modules are operated well below their maximum ratings.
Each RF power amplifier (PA module) is fully modular within itself and each module has a gain
equivalent to the entire gain of the transmitter (see Figure 2). Each PA module has it's own
preamplifier, Intermediate PA, Driver and PA section. The front end preamplifier on the PA
module monitors and provides soft startup, overdrive and VSWR protection for the module itself
(independent of the transmitter protection). The output stage of the module consists of three
amplifier "pallets" each consisting of two push-pull LDMOS FET amplifiers that operate in class
AB, and are combined in quadrature. The outputs of these pallets are further combined in a 3way combiner. The amplifier module is rated for 350 watts, and in the present four PA module
system is operated at a total transmitter power of 1 kW sync peak + 100 watts aural/sound. The
module is provided with a test jack for monitoring.
The amplifier output is fed to the bandpass filter and a directional coupler, which provides a small
sample of forward and reflected output power for metering, AGC and VSWR supervisory
functions. An additional sample is available for monitoring and transmitter setup. The transmitter
output then passes to the antenna system.
TRANSMITTER CONTROL
The control circuitry in this solid state transmitter is straightforward and simple. The use of
latching type relays ensures that the transmitter state (on/off, or trip status) is “remembered”
under power failure conditions. Interlocking is provided for loss of airflow and for over
temperature conditions. An additional interlock connection point is provided for interlocking the
transmitter to an external patch panel.
Facilities are provided on the control board for telemetry, status, and control connections to and
from a remote control system. These are available on 25 pin D-sub connector.
For remote control operation, simply press the REMOTE switch (LED illuminated). This places
+12V on Remote Enable line and allows the transmitter to be turned on and off via remote
control. In this mode the transmitter cannot be turned on locally but for safety purposes, the
transmitter can always be turned off locally while in REMOTE.
The Remote Enable +12V appears as an arming signal at J5-5. A momentary connection of this
+12V to J5-13 turns the transmitter ON, and momentary connection of the +12V to J5-8; turns the
transmitter OFF.
Control circuit power for the transmitter is supplied by two redundant power supplies wired in
parallel. The failure of either power supply will not affect the operation of the transmitter.
The transmitter's power supply consists of two ferro-resonant transformers each with dual
secondary windings. Each transformer secondary feeds a rectifier/filter and linear regulator
combination. The regulator modules are located inside the rear door of the transmitter and can be
removed for servicing by first disconnecting the two cables and then unplugging the module. This
can be done without turning off the transmitter.
A two pole fused disconnect or breaker is required for transmitter connection from line-to-line.
The transmitter is wired per Figure 5.
•
Press the OFF button on the control panel. Pull out the regulators so they are no longer
mating with their respective AC power connectors. Turn on the power supply breakers. Press
the ON button. Looking into the back of the transmitter DS6 and DS7 on the AC distribution
board should be illuminated (refer to figure 3). If the blower comes on and DS6 and DS7do
not, then the AC Distribution board needs to be bench tested.
•
Press the OFF button again. Install the regulators but disconnect the cables that mate at the
top of each regulator (connecting the regulators to the PAs). Turn on the transmitter.
Measure the voltage on the output connectors of the regulators. The voltage should be 28V
(±0.5V) for each regulator. Note: Since the regulators have no load, when the transmitter is
subsequently turned off it will take a while for the voltage to decay down to zero.
•
Turn off the transmitter. Reconnect the cables to the regulators. Turn the RF drive level
down as far as it will go at the appropriate OUTPUT LEVEL/RF OUTPUT adjustment on the
exciter. Alternatively, disconnect the drive from the output of the exciter. Turn on the
transmitter. Using a clamp-on current meter, measure the current going from the regulators to
the PA's. Measure the current going through the +28V supply cables and not the return
cables (some of the ground current may return through the transmitter chassis as opposed to
the return wires, causing the current reading to be lower than it actually is). The 28V supply
cables are the two lower wires in the cable assembly (Figure 4). These are accessible by
pushing back the protective covering on the cable. The front panel current meter (the digital
LCD meter) can now be calibrated for each PA module. (Remember that the modules are
numbered 1-4 from left to right across the front of the transmitter. This will be reversed when
looking into the rear of the cabinet.) The corresponding adjustment pot on the control panel
(PC board 20C2065G1) is listed below.
PA1
Pot R221
PA2
Pot R225
PA3
Pot R229
PA4
Pot R223
These adjustments can be accessed by opening the hinged control panel on the front of the
transmitter.
•
Disable the AGC using the front panel AGC Enable switch. Note: the AGC is disabled when
the LED on the enable switch is off. Increase the output power from the exciter until 100%
•
•
•
•
•
•
•
•
•
operating power in achieved. Use a thru-line type Wattmeter to measure the transmitter
power. Select FWD on the analog meter select switch and adjust R164 on the control board
until the forward power meter (analog meter) reads 100%.
To calibrate the aural power, refer to the RF detector board description and setup procedure.
Calibration of the reflected power metering and the VSWR cutback and trip is detailed next.
Note, this setup was done at the factory initially, and should not be adjusted unless absolutely
necessary. Conditions that would warrant this adjustment include the replacement of the RF
detector assembly or the control PC board.
Turn R130 fully CW and R138, and R128 fully CCW
The Reflected power meter reading corresponds to 10X the actual power reflected. That is,
when the reflected power meter reads 100%, this means 10% of the output power is being
reflected (ie: there is a VSWR of 1.9:1 at the transmitter output). (10dB match). To calibrate
the meter for this level, the forward sample port that feeds the RF detector circuitry for
metering is fed through a 10dB attenuator back to the reflected power input on the RF
detector board. To do this, disconnect the cable at the forward port of the output directional
couple and connect Reflected power sample cable through a 10dB pad to the forward power
port. This simulates having a 10dB mismatch on the output of the transmitter. Note: AGC
must be disabled during this procedure. Adjust R117 until a 100% reading is achieved on the
RFL power setting of the analog meter.
Change the attenuation from 10dB to 16db of the forward power into the reflected port on the
metering board. Adjust R138 so that the power just starts to cutback slightly
Adjust R130 so that the VSWR CUTBACK LED just turns on.
Change the attenuation to 13dB. The cutback circuit should cut the power way back. Adjust
R128 so that the transmitter trips and locks out with VSWR.
Now change the attenuation to 14 dB of forward power into the reflected port on the metering
board. Adjust R128 so that the transmitter does not trip and lockout with VSWR. You may
have to press reset, adjust the pot, press reset, adjust the pot, etc. Then repeat the previous
step to verify that the transmitter still trips with 13 dB of reflected power.
Reconnect the forward and reflected sample cables to the directional coupler as they were
before. Verify that the AGC buttons can raise and lower the power levels.
TABLE OF CONTENTS
1.
2.
INTRODUCTION .........................................................................................................................1
CIRCUIT DESCRIPTION..............................................................................................................2
Visual Forward And Combined Reflected Circuit Description ..............................................................2
Aural Forward Metering....................................................................................................................3
3. TEST AND CALIBRATION ...........................................................................................................3
Test Equipment For Board Tests On The Bench: ...............................................................................3
Test Procedure................................................................................................................................4
4. PARTS LIST................................................................................... Error! Bookmark not defined.
LIST OF FIGURES
Fig
Title
RF Detector Board (Photo)
Test Equipment Setup for Bench Test
Assembly Drawing
41D1607
Schematic Diagram
41D1607S
1.
INTRODUCTION
RF Power levels throughout the transmitter are sampled in directional couplers, and the resulting RF
samples are detected and appropriately processed to provide DC outputs corresponding to the amplitude
of the desired parameter of the input signal. These DC outputs contribute to the AGC/VSWR supervision
of the transmitter as well as the front panel metering.
The 41D1607G1 and 41D1607G3 dual RF detectors are designed for measuring forward visual/vision
signal, forward aural/sound signal and reflected combined visual and aural signal. Group 1 is for NTSC
and group 3 is for PAL. The circuitry provides DC outputs corresponding to the instantaneous
visual/vision forward and reflected RF levels at the back porch (blanking level) of the modulated signal, so
that the DC output remains proportionally constant regardless of the video signals to the transmitter. Two
virtually identical detector circuits reside on a single board for visual forward and reflected metering.
Detection sensitivity of the circuitry for reflected visual/vision power is approximately 10 dB greater than
for the visual/vision forward RF detector circuit. Group 1, (for NTSC) and group 3, (for PAL) differ only in
their colour subcarrier frequency, consequently in a few component values.
The aural/sound metering circuit takes a sample of detected video signal from forward port and provides
DC level proportional to the amplitude of the aural carrier. The sample of this DC level is used to
compensate visual forward reading affected by presence of the aural carrier at the forward port. The
reflected port does not have this compensation circuit so in reality reflected reading is combined visual
and aural power.
The 41D1607G2 and 41D1607G4 dual RF detectors are similar, but have identical detection sensitivities
for each circuit. Th ey are designed for use in parallel amplifier systems. Group 2 is for NTSC and group
4 is for PAL; again, these differ only in colour subcarrier frequencies. The two ports J2 and J3 are not
identical. J2 has aural metering circuit and compensation circuit for the presence of aural carrier at J2
port. J3 will measure combined visual and aural power unless special trap is used to reject aural carrier
Figure 1: RF Detector Board
2.
CIRCUIT DESCRIPTION
Drawing references: 41D1607 sheet 1 (Figure 3), and 41D1607S sheet 1 (Figure 4).
The visual/aural RF Detector board is fitted with two RF detectors, which respond to RF samples fed from
RF directional couplers mounted on transmission lines in the amplifier cabinets and/or on external probe
sections. The modulation envelope blanking level is measured because it remains constant, regardless
of the picture content of the transmission. Measurement sampling occurs during the back porch.
Both sections of the board are almost identically configured, except for the component numbering, system
gains and the function names given in schematic Figure 2. Because the same discussion applies to both
circuits, we will describe the first one only, but refer to the second one during the description by enclosing
the relevant component numbers in parentheses ( ).
VISUAL FORWARD A ND COMBINED R EFLECTED CIRCUIT D ESCRIPTION
(REFER TO 41D1607S SHEET 1)
The RF sample is applied to input J2 (J3) and is terminated by R2 (R34). CR1 (CR3) and Q1 (Q6) form
an envelope detector. CR1 (CR3) is forward biased slightly by R1 (R33) and R3 (R35) to overcome CR1
(CR3) conduction threshold voltage, thereby improving detection linearity. Q1 (Q6) is forward biased by
R3 (R35) as well, and when RF is applied, Q1(Q6) is driven in the direction of turn off during each
positive -going half cycle, thus causing its emitter voltage to become more positive, and in effect forming a
linear envelope detector.
C50 (C51) utilizes the lead inductances of CR1 (CR3) and Q1(Q6) to form a Tee network, which provides
a matching section that improves the UHF signal transfer between the devices.
Q1(Q6) and CR1 (CR3) have similar temperature coefficients, and the opposing connection of the two in
this back-to-back configuration, provides temperature compensation.
Finally, Q1(Q6) serves as a low impedance video source to drive the colour traps FL2, FL4 and aural
traps FL1, FL3 which remove the colour subcarrier burst and aural carrier from the back porch.
Subsequent downstream sampling circuits monitor the blanking level, therefore require a clean back
porch. The detected video signal is phase split by Q2 (Q7) to produce two 180° out of phase signals. The
inverted video signal, after being buffered by Q11(Q13), is fed to input pin 11 of sync separator Ul (U8).
Ul (U8), pin 7 is an open collector "mute" output, which switches off when adequate horizontal sync
pulses matching the setting of R28 (R57) are present, lighting CR2 (CR4) the "sync ok" LED. If a TV sync
signal is not detected, pin 7 collector goes low, and CR2 (CR4) is turned off. When sync is detected, the
sync output at pin 9 delivers a positive -going composite sync pulse, which turns on Q5 (Q10) whose
collector then goes low. If no sync is detected by Ul (U8), its pin 9 remains LOW, and Q5 (Q10) remains
off.
After the pin 9 pulse has finished, Q5 (Q10) turns off and its collector output goes high. This low-to-high
transition activates blanking multivibrator U2 (U7), and an active low pulse is fed to Q3 (Q8), turning it on.
Q4, C5, and U4A (Q9, C22, and U6B) form a sample-and-hold circuit that samples the signal originating
from the emitter of Q2 (Q7) and which is buffered by Q12 (Q14). Sampling occurs during the back porch,
and holds during the subsequent horizontal line. This DC sample is amplified in U4A (U6B).
Because a "single supply" op-amp is used at U4 (U6), the output seen on TP9 (TP10) will contain a small
DC offset which must be minimized because low level signals are near ground/earth potential. With no
RF input, this offset voltage is adjusted by potentiometer R10 (R42) as near as possible to zero. A
residual voltage offset of 10 to 20 millivolts can be expected.
Outputs from unity gain op-amps U4A, U4B(U5A, U5B) drive the forward (reflected) power metering
circuits, and provide telemetry and AGC (VSWR) signals.
Bench test calibration consists of adjusting the level to U4A (U5A) on R13 (R43) with calibrated, properly
modulated input: The forward input at J2 should be 200 mW in 50Ω, (J3 Reflected input 20 mW for both
the 41Dl607G1 ,3 boards, or for 41D1607G2,4 boards the J3 Combined input 200 mW), and the voltage
observed at TP1 (TP2) should read 4.0 volts DC for full scale calibration.
AURAL FORWARD M ETERING
A sample of the signal detected by CR1 from J2 is buffered by Ql and high-pass filtered by R90, C55 and
the input impedance of Q15. R92 and R91 set the base bias for Q15 while R93 and R94 set the gain of
the stage to approximately 4.7 for the 4.5 MHz (5.5 MHz) aural intercarrier signal. The wideband
visual/aural signal drives FL1, an aural bandpass filter. This filter is chosen to match the broadcast
standard used. C59 couples the filtered aural signal to common emitter amplifier Q17 which is direct
coupled to common base amplifier Q16. The bias for these stages is set by resistors R95, R96, R97.
C57 and C58 provide bypassing. Q16 is a current amplifier with L7 as the collector load and C60 provides
frequency compensation.
The aural signal is then fed to a peak voltage detector consisting of CR6, C63 and R102. U9A provides
DC amplification of the detected signal. Amplifier gain is set by potentiometer R104 such that the DC
level at TP8 is in the range of 7VDC. This provides enough "safety" range for the signal not to saturate
yet enough level to reliably give a 4VDC calibration at TP3.
3.
TEST AND CALIBRATION
TEST EQUIPMENT FOR BOARD T ESTS ON T HE B ENCH:
RF Detector test fixture, comprising a 12 volt DC power supply, suitable connectors for the board to be
tested, a signal generator, a modulator, and an amplifier good for 200 milliwatts output. An exciter will
suffice for the generator and modulator, but its output is good for a maximum +10 dBm (10 mW) therefore
requires an external amplifier, and the exciter aural output may be used as an unmodulated source if
required (A LARCAN exciter visual/vision section can not deliver unmodulated RF).
TEST PROCEDURE
•
•
For test setup, see Figure 2.
1.
2.
3.
4.
5.
6.
7.
8.
TEST EQUIPMENT REQUIRED
12 V power supply
UHF preamplifier (approx
200mWo/p).
Video Generator.
Modulator.
UHFUpconverter.
Oscilloscope.
Spectrum Analyzer.
VHF / UHF Two Way Splitter.
Connect board under test to power supply. Apply
•
ground on pin 7 & 8 of J2 and apply +12v (± 0.2 V) to
•
pins 3 & 4. Do not apply RF to J2 and J3 yet.
•
Adjust R111 max CW.
•
Adjust R10 to get a min voltage at Ul0-1 (TP9).
Check the voltage between U10-2 and U10-3. It
•
should be no more than 10 mV.
•
Adjust R42 to get a minimum voltage at U6-7 (TP10).
Check the voltage between U6-6 and U6-5. It should
be no more than 10 mV.
Set R104 in mid position.
Apply staircase modulated RF signal from UHF upconverter to J2 and J3 through splitter
according to Table 1. The signal should include aural carrier 10 dB lower than visual sync peak.
Check this level on the spectrum analyzer. Note: Make sure to set spectrum analyzer resolution
RBW to 300 kHz to see sync peak level.
Assembly Group
G1/G3
Connector
Visual Peak
Signal
[dBm]
J2
23
G2/G4
J3
13
J2
20
J3
20
TABLE 1.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Adjust R104 for 7.5 ± 0.5 V at TP8.
Adjust R107 for 4V at TP3.
Adjust R28 so that CR2 lights up.
Adjust R57 so that CR4 lights up.
Using the oscilloscope, check that there are positive 12V pulses at TP4 and TP5.
Check DC voltage at TP9.
VTP9 should be within 4.5V to 9.5V.
Check DC voltage at TP10.
VTP1O should be within 4.5V to 9.5V.
Turn off the aural carrier.
Adjust R13for4VatTP1.
Turn on the aural carrier.
Adjust R111 for4V at TPl.
Repeat steps 12 and 13 until voltage at TP1 stays the same with and without aural carrier.
Adjust R43 for 4 V at TP2 with aural carrier on.
Figure 2. Test Setup For Visual + Aural RF Detector Assembly.
TABLE OF CONTENTS
1.
2.
INTRODUCTION .........................................................................................................................1
CIRCUIT DESCRIPTION..............................................................................................................1
Front End Preamp. ........................................................................................................................1
IPA Module ....................................................................................................................................2
Pallet ..............................................................................................................................................3
Module Interface Board. ...................................................................................................................4
3-Way Splitter .................................................................................................................................4
3-Way Combiner .............................................................................................................................4
3. TESTING AND TROUBLESHOOTING..........................................................................................4
Front -End Preamp...........................................................................................................................5
Intermediate Amplifier (IPA) ............................................................................................................5
4. PARTS LIST................................................................................... Error! Bookmark not defined.
1.
INTRODUCTION
The PA module for the MX1000 is a high gain linear amplifier.
Each PA module includes its own preamplifier, intermediate
amplifier, driver amplifier and power amplifiers. The gain of
the module is equal to the gain of the entire transmitter. Every
PA module has its own on-board protection against overdrive,
excessive VSWR and over temperature. A single LED on the
front panel indicates the status of the module. Any fault will
cause this LED to turn off.
Figure 1: PA Module, MX1000
2.
CIRCUIT DESCRIPTION
FRONT END PREAMP.
The RF input to the module is via J1. U1 provides the amplification of the signal for this stage. This IC is
an 18dB gain broadband hybrid amplifier. The output of this stage to the following amplifier (IPA) stage is
through J2. A directional coupler HY1 provides a sample of the input power for a detector CR1, C2
through C4 and buffer amplifier U6B and associated components. A PIN attenuator circuit consisting of
CR2, CR3, R8 through R13 and C5 and C6 provides the means for controlling the signal gain through the
front-end stage. A higher voltage applied to this attenuator through L1 results in less attenuation through
the PIN attenuator and hence, more gain through the preamp unit. A further coupler HY2 provides an
output sample to a detector and buffer circuit (CR4 and U6C). The maximum gain of the front-end
preamplifier is approximately 8dB, however, in practice, the gain is adjusted to compensate for gain
differences in other stages such that the gain of each PA module is the same.
The three-way combiner circuit for the PA module incorporates a bi-directional coupler with detectors for
forward and reflected power on the module. These detected voltage samples for forward and reflected
power are fed into the front-end preamp through J4-7 and 14. Comparator circuitry is used to detect
either overdrive conditions or VSWR conditions. Since the circuitry is identical for both forward and
reflected, a circuit description will be given for the forward power circuit only.
U3D is configured as a comparator with the reference voltage being provided by the voltage divider
consisting of R44, 45, 46. Note: this level is preset. Values for this voltage divider should not be
modified. Doing so without prior authorization from factory service personnel will void any warranty.
When the detected voltage rises above the preset level, the output of the comparator U3D goes high, and
forces transistor Q1 to the "on" state through diode CR7. Other inputs to Q1 include the reflected
(VSWR) signal, an external mute signal and a power-up delay circuit consisting of U5D configured as a
comparator along with R47 through R50 and C20. The action of turning on Q1 causes the voltage on the
PIN attenuator, preset by R25, to be shunted through the transistor, thus increasing the attenuation of the
PIN attenuator.
Additional circuitry on the front-end preamplifier also drives the logic for the Green LED on the front panel
of the PA module. Output samples from each of the power amplifier pallets are monitored and compared
with preset voltages through comparators U2C, U2D and U3C. A failure of the output of any one of these
pallets will cause the output of U5A to drop and the LED (connected to J6) to be extinguished. Note: this
applies if the input RF signal is removed and thus results in no output from the module (as well as in the
case of an overdrive situation or VSWR cutback situation).
There are buffered signals for the various stages on the PA module that are brought to the front -end
preamp and routed through to the interface board on the rear of the PA module. These signals are
present on the 25 pin connector (intended as an on-site troubleshooting port). In the MX 1000
application, these signals are present but most are not
monitored by the transmitter's control circuitry.
IPA MODULE
The intermediate amplifier consists of two FET
amplifiers, type MRF181 paralleled in RF phase
quadrature, and operated in class A. Amplifier static
bias control and over-current protection is provided by
an industry-standard type µA723 regulator IC, U1.
The overall gain of the Intermediate Amplifier is a
nominal 15 dB over the band.
Figure 2: IPA Module
The input signal is split evenly by quadrature hybrid
splitter HY1. Each FET gate is matched with the equivalent of an L network followed by a π network.
Capacitors C100 and C110 provide DC blocking of the gate voltage. A couple of low impedance
microstripline sections along with adjustable capacitor (C101 or C111) to ground and the gate
capacitance of the FET form the L-C-L-C matching network for the input circuit. This matching
arrangement is good for operation from 470 through 860 MHz, adjustable capacitors C101 and/or C111
provides for a flat frequency response over the range.
The output circuit is similar except it uses narrower (higher impedance) microstriplines because the drain
impedance of the FET is higher. The output matching network is adjustable with variable capacitor C103
or C113. Again, this capacitor is adjusted only to provide flat response over the 470 to 860 MHz range.
An output coupling capacitor C104 or C114 completes the match to 50 ohms; two amplifier outputs are
combined in a quadrature hybrid HY2.
Bias to the gates of the FETs passes through R100 or R110 from balance controls RV100 or RV110. The
bias regulator Ul uses an µA723 (MC1723CD) to provide approximately 6½ volts to the gate bias controls
RV100 & RV110. Voltage divider R5, R6 provides the inverting input of the regulator error amplifier with a
sample of the output voltage, and the wiper of RV3 provides the non inverting input with its reference
signal which is an adjustable fraction of the 7.15 V built-in reference of the µA723. The adjustment of
RV3 therefore should be able to give an output within the range from zero to approximately 9 volts. R4,
C2, C1, R3, and C4 provide frequency-compensation and maintain regulator stability.
Drain current of the two FETs is sampled by the voltage drop across R7. When this voltage exceeds
approximately 0.5V at normal operating temperature (about 1.5 amps total FET current), Q3 begins
conduction and feeds voltage to pin 2 of the regulator to start its current foldback/limiter circuit.
The regulator reduces its output voltage, which in turn reduces the bias on the FETs, they decrease their
drain currents, reducing the voltage drop across R7 and over-current protection is achieved. CR1
protects Q3 emitter-base junction from current inrush to C3 and C107 charging during start-up.
PALLET
The following description applies to the
driver amplifier as well as the circuitry
used in each of the three sub-modules
comprising the final PA stage of the PA
module. The difference being that the
driver consists of a single device
amplifier (called a “half-pallet”) while the
final stage are based on dual FET
amplifiers with an integral 3dB hybrid
combiner. Referring to the schematic
diagrams (figures 14 and 16) one will
notice that even the component
numbering is similar. The following
description is for the dual FET version of
the amplifier (refer to fig 16).
Figure 4: Driver
The stripline balun developed at LARCAN is a practical implementation of the coaxial cable based
solution on a broadside-coupled horizontal stripline structure. It is made up of three printed circuit boards
of high dielectric material bolted together. Using this structure, very tight coupling can be achieved, thus
emulating the properties of a coaxial transmission line balun. With this arrangement, the characteristic
impedance and degree of coupling can be controlled through geometric dimensions. This circuit is the
subject of a patent application.
The amplifier pallet (full-pallet) couplers also include hybrid 3dB couplers as part of the multi-layer
stripline circuit. The resultant output of the coupler assembly is two pairs of equal and opposite phase
signals 90 degrees out of phase (that is, a set of signals at 0° and 180°, and a set of signals at 90° and
270°).
Transistors Q1 and Q2 are Lateral N-Channel Broadband Push-Pull Power MOSFETs. One side of the
amplifier is described.
Components C6 through C11 and C52 along with the associated printed
circuit traces form the matching network to the gate of the push pull
transistor Q1. L2 and R2 along with L3 and R3 are low frequency parasitic
arrestors. Similarly, C14 through C15 and C53 along with associated
stripline traces provide output matching on the drain of the device. C6, C8,
C16 and C18 also provide DC blocking of the supply and bias voltage. C7
is factory adjusted for a flat frequency response from 470 to 860 MHz.
DC power enters the module through a screw terminal connection and is
fed to the main circuit board through a series of jumpers. 28V is fed to the
drains of the FETs via L5 and L6 with bypass capacitors C13, C25, C20,
C22 and C28. Bias for the devices is via L1/L4 with bypass capacitors C1,
C2, C5 and C12. The bias voltage is adjusted via R12 and R11, from a
regulated source provided by Ul. R12 sets the overall bias and R11
provides adjustment for balance between Q1 and Q2. Thermistors R21 and R22 provide thermal stability
for the bias.
MODULE I NTERFACE BOARD.
This PC board is located on the rear of each PA module. The RF input and DC input to the module
enters via this interface board. Four fuses are located on this board. Three fuses are in line with the 3
output PA pallets and one with the front end, IPA and driver modules. These fuses serve to protect the
circuitry from damage in the event of a device failing in the short circuit condition. This is part of the “soft
failure" mechanism of the PA modules. Because the normal failure mode of a transistor is a short circuit,
and we desire to keep the rest of the PA module functioning in the event of a failure, the fuse effectively
disconnects the failed circuit from the regulator, allowing it to supply the rest of the module.
The interface board performs a number of other signal routing functions. Various signals from the different
stages of the module are routed through this board to connectors. In the case of the MX1000, many of
these signals are not routed any further, but are present on the connector (J3).
3-W AY SPLITTER
The three-way splitter is a stripline implementations of a 1.76dB hybrid/3 dB hybrid combination. It is a
mechanical structure consisting of 3 PC boards sandwiched together to form the stripline structure. The
middle layer board thickness along with the trace locations determine to the largest extent the coupling.
J4 feeds a 1.76dB splitter. The input power to this splitter is divided 1/3 – 2/3 between the two outputs.
The 1/3 output is fed to J3 and the 2/3 output is fed to a further 3dB hybrid coupler. The two outputs of
this coupler are fed to J1 and J2. The termination load for the reject port of the 1.76dB splitter is at the far
end of the board from J4 and the termination load for the 3dB coupler is located at the edge of the board
between J2 and J3. J5 is connected to a directional coupler on the input to the splitter and is not used in
this configuration.
3-W AY COMBINER
The three-way combiner is essentially the mirror of the 3-way splitter. J1 and J2 are coupled to the inputs
of a 3 dB hybrid coupler. The output of this combiner is fed to the input of a 4.77dB hybrid coupler along
with the input from J3. The output of this coupler appears at J4. R6 serves as the balance load for the
3dB coupler while R7 serves as the balance load for the 4.77 dB coupler. Each of the inputs to this
combiner have a directional coupler and detector circuit that feeds a DC sample of the output of each
pallet to the sensing circuitry on the front-end module. As well, a directional coupler on the output of the
combiner has detectors for both the forward and reflected power samples of the output. All the
information fed back to the front-end appears at J11. Additionally, a second directional coupler provides
an RF sample that is fed to a front panel test point via J5.
3.
TESTING AND TROUBLESHOOTING
Basic troubleshooting of a PA module is as follows. The front panel
LED is extinguished if one or more output amplifier pallet levels are
lower than nominal preset level. As mentioned earlier, if the drive is
removed from the module(s), the output of the amplifiers also satisfy
this condition and thus the LED will be off. In this case, there is
nothing wrong with the amplifier. Therefore, if all the LEDs are off,
the first place to look is at the output of the exciter.
If a fault condition exists (LED off) on a single module, the first place
to check is the PA module interconnect board where all the fuses are
installed. A blown fuse will most often indicate a defective amplifier
pallet. Most times, this will be the problem and replacing the
defective amplifier and fuse will rectify the problem. If, however,
there are no blown fuses, there are other areas to check.
Figure 6: Fuses
The front panel current meter will give an indication of the current drawn by the modules in comparison to
one another both under drive conditions and under static bias conditions. Check the current under drive
conditions for overdrive situations and under static bias conditions (no drive) for amplifier stage failure.
Check for potential connector problems causing either no drive to a module (input connector) or VSWR
(output connector) problems. Also, if you suspect an over temperature condition, be extremely careful
when pulling out a module as the heatsink may be too hot to hold onto comfortably.
The following procedures are essentially the same procedures used during factory testing. Basically, if
there is no suspected problem with a particular stage, we would recommend not performing these
procedures.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
FRONT -END P REAMP
Short Pin J4-10 to ground (this can be accomplished by placing a small jumper across J4-10 and J48). This simulates a good thermal switch.
Connect a +28V power supply to E1 and ground.
Apply a 0dBm (1mW) RF input to the amplifier.
Turn R25 fully clockwise. The preamp should have minimum gain (approx. 7dB). Adjusting R25 from
one extreme to the other should vary the gain 4dB.
Check RF output telemetry. There should be 1.5V ±0.5V at J3-12.
Check the RF input telemetry. There should be 1.0 ±0.2 V at J3-13.
Check the RF attenuator voltage telemetry. There should be 5.4V ±0.2V at J3-1
Check Thermal switch status indication. J3-4 should be 0V.
Remove the jumper from J4-10 to J4-8. (This simulates the thermal switch opening). The voltage at
J3-4 should be high (4 Volts ±0.5V) and J3-1 should be 0V.
Replace the jumper across J4-10 and J4-8.
RF Mute check: Connect a variable supply, to J3-2. Gradually increase the voltage until the gain
drops by 30dB or more. The applied voltage should be approximately 2.5 volts.
Reflected Power Cutback check: Connect the variable supply to J4-9. Increase the voltage gradually
until the gain drops by 30dB or more. The voltage should be approximately 4.0Volts ±0.2V. This
same voltage should also be present at J3-14. J3-6 should be 4.0 volts.
Overdrive Cutback check: Connect the variable supply to J3-7. Increase the voltage until the gain
drops by 30dB or more. The voltage should be 7 volts ±0.5V. The voltage at J3-11 should be the
same and the voltage at J3-7 should be 4.0 volts.
Set the adjustable supply to 2 volts. Connect this voltage to J4-1, J4-3 and J4-5 simultaneously. J26 and J3-5 should be high. Disconnecting any one or more of J4-1,3 or 5 should cause both J2-6 and
J3-5 to go low (0V).
INTERMEDIATE AMPLIFIER (IPA) B ENCH T EST PROCEDURE:
This amplifier must be mounted on a properly sized heatsink for testing.
• Connect a suitable load to the output of the IPA.
• On the IPA under test, set RV200 fully clockwise and set RV110 fully counter-clockwise.
• Set variable power supply to 28.0 volts and set its current limit to 1 ampere.
• Apply the +28V to the feedthrough capacitor of the IPA shield box.
• Adjust RV3 to achieve 6.5 ±0.2 volts at the junction of R5 and RV100.
• Adjust RV200 to achieve total current draw of 500 ±20 mA.
• Check that the junction of R100 and CR100 measures between 3.5 and 5.5 volts.
• Adjust RV110 to raise total current draw to 1000 ±50 mA.
• Check that the junction of R110 and CR110 measures between 3.5 and 5.5 volts.
• Increase the power supply current limiting to 2.2 Amps.
•
•
•
•
•
Increase RV3 clockwise slowly and check that the maximum current limits itself at 1.6 ±0.1 Amp but
do not allow current to go above 2 amps while performing this test.
Reset RV3 to achieve 6.5 ±0.2 volts measured at the junction of R5 and RV100.
Check balance of the two transistors with a voltmeter connected between the hot sides of C105 and
C115; difference voltage should be less than 3 mV.
Apply RF drive (max. +18dBm to IPA) and adjust C101, C103, C111, and C113 for minimum
frequency response ripple and flat response. Gain should be a minimum of 15 dB with maximum
variation less than 0.5 dB over the frequency range 470 MHz through 860 MHz (Note: IPA output will
then be about +33dBm or 2 Watts, so make sure you properly protect your test equipment).
If roll off at the higher frequencies prevents meeting this gain-bandwidth specification, it may be necessary to
replace either C103 or C113 or both with a higher value; use variable capacitor made by Johanson, part #
16E2320-2, which is 2.5 to 10pF.
TABLE OF CONTENTS
1.
2.
3.
4.
INTRODUCTION .............................................................................................................1
BLOWER REPLACEMENT ..............................................................................................1
COMBINER AND REJECT LOAD .....................................................................................1
THERMAL SWITCH AND AIR SWITCH ............................................................................2
Thermal Switch ...................................................................................................................2
Air Switch............................................................................................................................2
5. PARTS LIST....................................................................... Error! Bookmark not defined.
LIST OF FIGURES
Fig.
Description
1.
Roof of Transmitter
2.
Access to Blower
3.
Thermal Switch/Air Switch Location
1.
INTRODUCTION
The following description, while described as the module housing for the transmitter, in essence,
comprises the additional assemblies and circuits that are not included in the other assemblies
described in this manual. They include such assemblies as the Blower, the 4-way combiner and
reject load assemblies for the overall output, the various interface circuitry and the protection
circuitry. The “housing” is basically the assembly that brings all these items together.
2.
BLOWER REPLACEMENT
The Blower is located on the top of the module housing. It is accessible through the top of the
transmitter. The blower is a backward curved motorized impeller. The motors have no
adjustments and need no maintenance. The blower motor bearing life should be on the order of
100,000 hours. Should the blower fail for any reason, the replacement is relatively simple. The
entire blower and motor assembly can be removed through the top of the cabinet.
Figure 1: Roof of Transmitter
3.
Figure 2: Access to Blower
COMBINER AND REJECT LOAD
The 4-way combiner used in the transmitter is basically a combination of three 3dB hybrid
couplers. Two couplers form the first level of combining and a third combines the outputs of the
first two for the final output. These combiners require balancing loads, or reject loads. The loads
are located in the module housing on an assembly similar to the module assembly. The Reject
load assembly is within the cooling air plenum and comprises all three reject loads for the
combiners. This reject load assembly is not removable when the transmitter is under power and
as such incorporates SMA connectors and is held in place additionally by screws through the rear
of the module housing. A sample of the input to each of the loads is provided on the front panel
of the reject load assembly. These samples can be used for setting up of the 4-way splitter.
Phase and gain of each power amplifier signal path can be adjusted to minimize the power in
these reject loads.
4.
THERMAL SWITCH AND AIR SWITCH
THERMAL SWITCH
The thermal switch is located on the air duct
between the module housing and the blower. It
can be accessed by opening up the control panel.
The thermal switch, through its mounting on the air
duct essentially monitors the outgoing air
temperature of the module housing. The metal in
the duct itself serves to ‘average’ the temperature
in the duct. It is connected to the TEMP interlock
circuitry in the control electronics.
Figure 3: Thermal Switch/Air Switch Location
AIR SWITCH
The Airflow switch consists of a power resistor mounted back to back with a thermal switch. The
air that flows through the transmitter flows across this assembly, cooling the resistor. If the airflow
is compromised, the resistor is not cooled properly and thus heats up. At a certain temperature,
the thermal switch will open, shutting off the power supplies and thus protecting them from
damage. The thermal switch mounted on the resistor should not be confused with the
transmitter thermal protection.
The air switch is designed to detect the presence of air flow throughout the normal operating
temperature range of the transmitter and in fact operates, under normal conditions at a much
higher temperature than the maximum operating temperature of the transmitter itself. The sole
purpose is to detect the presence of air flow, and in the case of reduced, or no air flow, the
resistor/thermal switch combination overheats and shuts off the supplies. WARNING: AC
VOLTAGE IS PRESENT ON THE AIR SWITCH RESISTOR. DO NOT REMOVE THIS
ASSEMBLY WITHOUT FIRST DISCONNECTING AC FROM THE TRANSMITTER.
TABLE OF CONTENTS
1.
2.
INTRODUCTION .............................................................................................................................1
CIRCUIT DESCRIPTION..................................................................................................................1
TEST AND TROUBLESHOOTING....................................................................................................1
General...............................................................................................................................................1
Troubleshooting ..................................................................................................................................2
Splitter Setup ......................................................................................................................................2
4. PARTS LIST....................................................................................... Error! Bookmark not defined.
1.
INTRODUCTION
The 4-way splitter provides four evenly balanced, equal amplitude, properly phased signals to each of the
PA modules in the transmitter. The intention is to provide the ability to fine match the phasing and gain of
the amplifiers such that they combine with the minimum of reject power. It has been found that normal
production tolerances do not cause wide variations in phasing between amplifiers and thus the control over
the output phase is limited to a relatively narrow range. At different channels, some touch-up of phasing
might be desireable in order to finely balance the PAs, although, it is not absolutely necessary.
2.
CIRCUIT DESCRIPTION
The RF enters this splitter via J5 and is applied to a PIN attenuator circuit comprised of CR1 and CR2 and
associated circuitry. The attenuator voltage to this circuit is applied through L1 via buffer amplifier/ inverter
Q1. A higher voltage at E2 results in more attenuation through the PIN attenuator. E2 is fed from the
transmitters AGC/VSWR circuitry.
The signal at the output of the PIN attenuator is fed to a hybrid 3dB coupler HY1. The two outputs from HY1
are fed to two more hybrids HY2 and HY3. The result is four outputs, equal in amplitude but differing in
phase. Each of the four signals is then passed through a phasing network and a further PIN attenuator for
the purpose of balancing the transmitter phase and gain overall. All four balancing circuits are identical
therefore only the circuit that supplies PA1 will be described.
The phasing adjustment is accomplished by using two varactor diodes CR100 and CR101, connected to the
output ports of a 3dB hybrid coupler HY4. If the impedance of these pure reactances is kept equal, the
signal is reflected back through to the isolation port of the hybrid with a change in phase and minimal loss.
The reverse bias on the varactor diodes is controlled through R101 and R102/R103. Attenuation adjustment
is controlled by varying the bias across CR102 via R108 through R111. This has the effect of shunting
some signal to ground. R110 controls the coarse level adjustment and R109 controls the fine adjustment.
U1 is a signal buffer amplifier. The signal is then passed through a final coupler which provides a sample to
a detector circuit and to the output connector J1.
TEST AND TROUBLESHOOTING
GENERAL
Because the splitter, in its normal operation provides the phasing and balance for the modules in the
transmitter, often times, if the balance between modules is incorrect, the splitter is the first suspected
problem area. One must be very careful troubleshooting under these conditions. What may be suspected
as a gain or phase imbalance can simply be a problem with a PA module. In addition, in the field it may be
difficult to quantify phase relationships between signals without a network analyzer. As mentioned
elsewhere in this manual, the transmitter has been delivered to site in a fully functioning condition. As
designed, the phasing controls in the splitter circuitry will allow up to approximately 30 degrees of phase
shift. The bulk of the phase relationship between the signal is developed within the hybrid splitters
themselves. Additionally, the gain controls on the splitter is only for fine matching of the module outputs.
TROUBLESHOOTING
If trouble is suspected with the splitter unit itself, the following checks may be done to pinpoint the cause of
failure.
•
•
•
•
•
Turn off the transmitter
With +12V connected to E1, verify that there is +8V (±0.1V) at pin 3 of VR1.
Disconnect the AGC signal to E2.
With signal applied at the input use a spectrum analyzer, to verify that there is signal at each of the four
output ports. Note; if one of the output ports is significantly lower (10dB) than the rest, this may indicate
a problem in that particular circuitry.
With a variable supply connected to E2, verify that the output levels of each port drop at least 30dB with
a voltage of 3.0 Volts.
SPLITTER SETUP
Fine balancing of the splitter outputs is accomplished with the transmitter operating at full power. Refer to
Figure 1 below. Firstly, the phasing and gain balance must be done between the inner level of combining,
that is between PA1 and PA2 and between PA3 and PA4. Then, carefully, the phasing must be done
between the PA1/PA2 combination and the PA3/PA4 combination.
The simplest way to balance the phase and gains is to monitor the reject
load power. On the front of the reject load assembly, there are various
sample ports for such purpose. The relative phasing and gain is adjusted
to minimize the signal level at these ports.
•
•
•
•
•
•
•
•
Balance all four PA output levels. This is best done with a spectrum
analyzer connected to each sample port in turn and adjusting R110,
R210, R310 and R410 to adjust the level of its respective PA module
output.
With the transmitter operating at full power, connect a spectrum
analyzer to reject load sample port for PA1/PA2. See figure 3.
Adjust either R101 or R201 (one or the other, not both) to minimize the
measured signal at this sample port.
Connect the spectrum analyzer to reject load sample port for PA3/PA4.
Adjust either R301 or R401 (one or the other, not both) to minimize the
measured signal at this sample port.
Connect the spectrum analyzer to the transmitter overall reject load
sample port.
Carefully adjust phase adjustment pots R101 AND R201 together to
minimize the measured signal at this sample port (alternately
R301/R401 pair can be adjusted instead).
Repeat the above steps to further reduce reject levels. Note: do not
use the gain adjustments to attempt to minimize reject load power.
*
R97 R98 C37
R95 R96 C36
R93 R94 C35
R91 R92 C34
R89 R90 C33
R87 R88 C32
R85 R86 C31
R83 R84 C30
R81 R82 C29
R79 R80 C28
R77 R78 C27
R75 R76 C26
R73 R74 C25
Rx Ry Cx
FIGURE 1
PWR
U2 - U6
11
TABLE OF CONTENTS
1.
INTRODUCTION .............................................................................................................1
MX1000 Power supply. ........................................................................................................1
Linear Regulator..................................................................................................................1
2. CIRCUIT DESCRIPTION..................................................................................................2
Rectification ........................................................................................................................2
Regulation Circuitry .............................................................................................................2
Control Circuitry ..................................................................................................................2
3. TESTING AND TROUBLESHOOTING..............................................................................5
4. PARTS LISTS ..................................................................... Error! Bookmark not defined.
1.
INTRODUCTION
MX1000 POWER SUPPLY
The MX1000 power supply consists of two transformers, each with dual (isolated) secondary
windings. Each power amplifier module is fed from a 60A linear voltage regulator. The output
voltage of each regulator is 28 Vdc. The input of the regulator assembly fed from the secondary
of the ferro-resonant transformer secondary winding is 35 Vac. The AC power to the
transformers is supplied via a contactor on the AC distribution board. This contactor is controlled
through the transmitter’s control board, ensuring that all interlock and overload conditions are
observed.
LINEAR R EGULATOR
The 60A linear voltage regulator is a ‘generic’ term for the entire plug-in assembly that performs
more than simply a regulation function. In essence, the Linear regulator assembly is an
independent power supply (less the transformer), performing rectification, regulation and self
protection. Assembly is accessible through the rear of the transmitter and can be removed from
service without turning off the transmitter. (For the purposes of description in this text, the ‘front’
of the linear regulator will be designated as the end with the handle, which is in actuality, located
at the rear of the transmitter). Obviously, removing a regulator will disable the associated power
amplifier and result in a lower output power. The AC input to the regulator is fed through the rear
of the regulator and the control, status and telemetry connections as well as the DC output fed to
the PA is located at the front of the module.
Figure 1: Linear Regulator Assy.
2.
CIRCUIT DESCRIPTION
The linear regulator assembly incorporates the following circuitry:
• A semiconductor-controlled rectifier bridge, the input filter capacitor and power resistors (Q1,
C1 and R63, R64 respectively). This circuitry is shown in block A on the schematic diagram.
• The Voltage Regulator itself (block B).
• The control circuitry (block C,D,E,F,G )which provides a few different functions including
over-current protection, over-voltage protection and power-on and reset functions.
R ECTIFICATION
Refer to block ‘A’ on the schematic diagram 40D1680S.
Rectification of the AC from the transformer secondary winding is performed by a semiconductorcontrolled bridge (SCR) rectifier, Q1. Capacitor C1 performs the filtering function. The
advantage of using a semi-controlled rectifier bridge instead of a conventional rectifier bridge is
significant. In normal operating conditions the bridge is constantly on because the opto-coupled
triacs, U33 and U34 are active. Thus Q1 behaves as a conventional rectifier bridge. In the case
of serious damage to the regulator unit the control can isolate the transformer secondary from the
rest of the transmitter by turning off the bridge (turning on U32). The power resistors R63, R64
are bleeder resistors, to safely discharge filter capacitor C1, when the unit is pulled out of the
transmitter.
R EGULATION CIRCUITRY
Refer to block ‘B’ on Schematic Diagram 40D1680S.
The voltage regulator circuitry consists of a low current linear voltage regulator, U1 utilizing an
external high power pass transistor, giving the regulator the required current capability for this
application. The combination of pnp transistor Q3 and npn power transistor Q2, creates the
equivalent of a high power npn pass transistor.
OR gate U25d activates, as required by the various overload commands from the control circuitry,
The output of this gate is applied to the internal shut down circuitry of U1-2. The command for
over-voltage shutdown is applied through U25d-12 and the command for over-current is applied
through U25d-13.
The output voltage setting for this regulator is provided by R18, R19 and R20. Additional
regulator output filtering is provided by C8 through C12
CONTROL CIRCUITRY
Control Circuit Operation
a.
Over-current.
Whenever an over-current or short-circuit condition occurs the control
circuit will shut down the output of the regulator, wait for 3 seconds
and try to restart. A fault is indicated by two LEDs lighting up, a red
LED (previous trip) which latches on showing that a trip has been
recorded and counted and a yellow LED (over-current) which is on for
the 3 second shutdown duration only. After three trips a red LED
(lockout) will come on until a reset command is received, resetting all
counters and restarting the cycle.
b.
Over-voltage
The operation of the overvoltage protection circuitry is much the same
Figure 2: Front
Panel Indicators
as that of the overcurrent circuitry with a couple of exceptions. One of the common
causes of failure in a series linear regulator is the short circuit of the series pass
transistor. Once the pass transistor has shorted, there is no way to shut down the
regulator output (to prevent over-voltage damage to the power amplifiers), hence the
SCR bridge that effectively disconnects the entire regulator from the transformer
secondary. When the over-voltage protection circuitry detects an over-voltage condition
the circuit shuts down the output of the regulator for 3 seconds and then tries to restart
the regulator. The fault is shown by two LEDs lighting up, the red LED (previous trip)
which latches on showing that a trip has been recorded and counted and a yellow LED
(over-voltage) which is on for the 3 second shutdown duration only. After three trips a
red LED (lockout) will come on until a reset command is received, resetting all counters
and restarting the cycle. In the event that the series pass transistor short circuits, turning
off the regulator IC will have no effect. In this case, additional control circuitry will shut
down the rectifier bridge isolating the regulator. A red LED (Q2 short-circuit) comes on.
A local reset switch for this circuitry is available for restarting the regulator (if the pass
transistor is indeed short circuited the circuitry will again shut down the regulator showing
the same fault condition). In this case the regulator must be serviced and Q2 replaced.
Until the necessary steps are taken to do this, the damaged regulator is safely isolated
from the rest of the transmitter.
c.
Power ON Reset and Master Reset
The regulator assembly utilizes control voltages supplied by the transmitter control power
supplies. These are supplied via a connector on the front of the regulator module. In the
event that these ‘auxiliary’ voltages are removed from the circuit the regulator control
circuit shuts down the rectifier bridge, isolating the regulator. This situation could occur if
either the auxiliary power supply fails or if the 15 pin control connector is disconnected
leaving the unit without the auxiliary voltages. When the voltages are reapplied, the
circuitry sends a power-on reset pulse, setting all counters and protection circuits back to
original conditions. The same effect occurs when the master reset switch is pressed and
released.
Over-current protection (refer to block C on schematic diagram 41D1680S)
Along with current transducer S1, block C on the schematic contains the over-current protection.
The current information from S1 is amplified and compared to a threshold determined by the
setting of R51. When the current information reaches the threshold level, the output of
comparator U6 goes high (0 to 10V). U3 is
a buffer amplifier that is used to distribute
Pin (U3) Output function
the over-current status to various other
pin 10
front panel status LED (overcircuits within the regulator (see table)
current ) and via inverter U20d to
over-current event counter U14a.
Whenever an over-current event happens,
pin 2
activates the OR gate U25d
the comparator output toggles (U6-6) and
shuting down the regulator.
the positive level through U3 (pin 6) is
pin 4
starts the timing circuitry (see
transferred through the closed contacts of
block E ).
K1 to the gate of Q7. Q7 turns on and R35,
pin 6
activates the locking circuitry.
R41 and R43 form a voltage divider latching
U6 into the ‘tripped’ state. When a reset
command is issued relay K1 is activated, the gate of Q7 discharged and the circuit comes back to
its original state.
Over-Voltage Protection (refer to Block D on Schematic diagram 41D1680S)
Over-voltage condition is sensed by U4. This is a programmable voltage sensor. The threshold
over-voltage reference is set by the voltage divider consisting of R5, R21 and R22 (the threshold
is set by the following formula: V= 2.6 [1+ (R5+R21)/ R22] ). An over-voltage condition causes
the output of U8 (pin8) to go high. This triggers flip-flop U10a. Once set, the flip-flop output (pin
6) stays high until a reset pulse clears the flip-flop. The output of the flip-flop activates a yellow
LED (over-voltage indicator CR5), the over-voltage counter, U14b, the ‘trip recorded’ circuit of
U29b and the regulator shutdown circuitry of U25d.
The over-voltage circuitry is reset by U12 as follows: Once the over-voltage disappears, the
output of U4 returns to zero, pin 5 of AND gate U2b becomes logic 1. The signal at pin 4 of this
gate is connected to the output of U10a (already set to logic 1). After a delay determined by the
timing circuitry (see block E ), pin 3 of U2b goes high triggering U12 and resetting U10a. The
regulator will restart. If the fault is still present the over-voltage trip will re-occur and event
counters will allow three overloads before the lock out circuitry shuts the regulator down.
In the event that the regulator is unable to shut down the output due to pass transistor short
circuit, the over-voltage shutdown circuitry will shut down the regulator but it will have no effect
on the output voltage. The output of U4 cannot return to zero in this case and pin 13 of U2a is
high (via inverter U20e) instead of pin 5 of U2b. After the timing circuitry delay, pin 1 of AND gate
U2a is set high, thus causing its output to go high. The output of flip-flop U10b is set and stays
high until reset via S2 ( Q2 FAIL RESET ). The output of U10b (pin 10) activates solid state relay
U32 . This removes drive from U33 and U34, turning OFF the bridge. The regulator circuitry is
now fully isolated from the secondary of the transformer and the rest of the transmitter.
Timing and Counting Circuitry (refer to Block E on Schematic diagram 41D1680S)
When overloads occur OR gate U25C triggers timer IC U26. This OR gate is triggered on pin 10
in the case of over-voltage trips and on pin 9 in the case of over-current trips. Once triggered the
timer releases a train of pulses to counter U28b. AND gates U30a, U30b and U31a monitor the
outputs of the counter and when all outputs are high U31a triggers the internal reset circuitry to
restart the regulator.
If the overload event was an over-current, U31d enables timer IC U16 (see block G). This IC
issues a pulse activating Q4, opto-coupler U15 and relay K1. The relay discharges the gate of
MOSFET Q7, releasing the over-current protection. Since relays are inherently slow devices,
opto-coupler U15 holds the shutdown pin of the regulator U1 high during the reset period. This
prevents serious over-current conditions on the output of the regulator from causing damage
during this transition period when the over-current protection circuit is resetting.
If the overload event was an over-voltage the output of U31a removes the shutdown condition
from AND gates U2a/U2b allowing the regulator to return to operation.
Each of the inputs to U25c are driven by an AND gate (U30d and U30c). These gates form part of
the three-shot lock-out circuitry. Binary counter U14a counts three over-current events and U14b
counts three over-voltage events. As long as the number of trips is less than three the outputs of
U31c and U31b are logic 0, the outputs of inverters U27e and U27d are logic 1 and over-current
or over-voltage trips are transmitted through the AND gates U30d/U30c. Once either of the event
counters reaches a count of three, the output of AND gate U31c or U31b goes high and the
internal reset circuitry is disabled . When the overload count reaches three LED CR8 (lockout )
turns on. A master reset is required to restart the regulator circuitry in this case.
Power-On and Master Reset Circuit (refer to Block F on Schematic diagram 41D1680S)
Whenever the control power supply from the transmitter (+ 12v) is disconnected and reconnected
to the circuitry, a power-up master reset is initiated. Q5 is activated after a delay given by
capacitors C36-C39 and divider R78, R74. K2 triggers the timer U18 which issues a mater reset
pulse. K2 can also be activated directly by pressing and releasing the master reset switch SW1
on the regulator.
Additionally, the main control board of transmitter can issues a reset command on pin 1 of
connector J1 (operator pressing tx front panel reset button). This external reset command will
only have an effect only if an overload trip has been recorded and is disregarded otherwise. In
this case U19 activates relay K2.
3.
TESTING AND TROUBLESHOOTING
With the exception of replacing the pass transistor in this circuit, repair of the circuitry on these
units in the field is not recommended. Any adjustments provided on the module are for factory
settings only. Modification of these settings should not be attempted in the field as damage to
other sections of the transmitter may occur.
To remove a regulator module, first unplug the control cable (ribbon cable). This shuts off the
regulator. Then unplug the DC cable that feeds the PA module and pull the module out of the
housing. Support the bottom of the regulator as the slide mechanism is shorter than the regulator
itself and the regulator may drop suddenly, potentially damaging the AC input connector.
TABLE OF CONTENTS
1.
2.
3.
4.
1.
INTRODUCTION .........................................................................................................................1
CIRCUIT DESCRIPTION..............................................................................................................1
TESTING AND TROUBLESHOOTING..........................................................................................2
PARTS LIST................................................................................... Error! Bookmark not defined.
INTRODUCTION
In order to minimize the amount of wiring in the transmitter, a single circuit board was used to distribute
the AC power and various DC control voltages throughout the transmitter. The circuit board is mounted
on the AC circuit breakers behind the circuit breaker panel. On later models of the MX1000, the control
power supplies are also mounted on this panel.
2.
CIRCUIT DESCRIPTION
The AC from the mains terminal block is distributed to the various power supplies and the blower via this
board and the breakers. The control power supplies receive their AC power via fuses Fl through F4 on J8
and J9. The three control voltages from these supplies come into the board on J8 and J9 as well. Each
of the voltages is monitored by voltage monitor ICs U3, U4, and U5. If one of the voltages fail, the PS1
FAIL or PS2 FAIL LED will illuminate. In addition, these control supply failure signals are routed to the
transmitter control board.
Each of the control voltages from the control power supplies is diode-ORed. Note that a single control
power supply can power the transmitter on it's own. Dual supplies are provided only for redundancy.
The AC to the transmitter blower and to the two power supplies is routed through circuit breakers CB1
through CB3. The BLOWER ON command is applied to this board on J8-39 from the tx control board.
An emergency interlock is provided for interlocking the transmitter to a building fire alarm system. This
interlock disables the transmitter blower as well as the power supplies (not the control power supplies).
The connections to this interlock are on J7. The interlock can be bypassed via JP1. K6 controls the AC
to the contactor relay K3 which provides AC to the blower at J2-2 and J2-3. The AC that supplies the
blower, also supplies power to the airflow switch.
The voltage applied to the blower also arms the power supply contactors K1 and K2.
The TX-ON command is applied through J8-37 from the transmitter control board. This signal energizes
K4 and voltage is applied to the power supply contactor coils of K1 and K2 via the step start thermal
interlock circuits and the breaker auxiliary contacts.
The AC to the power supplies is applied through a step-start circuit to minimize the inrush currents
associated with the ferroresonant power supplies. This step start circuitry consists of a resistor in series
with the transformer that is shorted out after a predetermined delay period. A solid state relay is used to
short the resistors allowing full supply voltage to be applied to the power supplies. In the event of a
failure in this timing circuit there is a thermal cutout switch mounted on the step start resistors. These
thermals will remove the power to the power supply contactor coils, thus removing power from the supply.
The step start timing circuit for one power supply will be described, the second circuit is identical. When
AC is applied to the surge The step start timing circuit for one power supplyresistors, AC is applied to
opto isolator U2-3 (U2-4). This opto-isolator applies voltage to the timing circuit consisting of R5 and C5
(R16/C11). When the voltage across the capacitor reaches a predetermined level as set by the voltage
divider R10/R11 (R13/R14), the output of comparator UlA (UlB) goes high causing the solid state relay K7
(K5) to turn on, shorting out the surge limiting resistors.
3.
TESTING AND TROUBLESHOOTING
This board is essentially an interconnect circuit for the transmitter and, as such there are not many circuits
on the board to require service.
Much of the troubleshooting that can be done with this circuit is detailed in the installation section of this
manual. The troubleshooting can be done by simply observing which LEDs are illuminated and
determining where the problem lies. Refer to figure for the location of the LEDs and to the schematic
diagram (figure ) for their function.
DS 11 and DS12 indicate the presence of AC on the inputs to the circuit breakers CB1 through CB3.
DS5 indicates the presence of a blower command. DS8 indicates that the blower contactor K3 is closed.
DS6 and DS7 indicate that power supply contactors (K1 and K2 respectively) are closed. DS9 and DS10
are illuminated during the startup inrush limiting period, indicating essentially that the inrush resistors are
in circuit. Note that these resistors are provided to limit the inrush caused by the magnetizing current of
the ferroresonant transformers and protect the contactors from damage due to these high currents as well
as prevent inadvertent breaker trips. Should the inrush circuitry fail to function properly, leaving these
resistors in circuit and dissipating power, the thermal cutouts mounted on the surface of the resistors will
open, causing the contactors to open. DS1 and DS2 indicate this thermal cutout condition should it
occur.
DS11
R46
J8-37
R45
TX ON CMD
L1
+12V
L1
L1
1uH
DS12
L2
11
L2
THERMAL 1 FAIL
J13
R1
NC
NC
J15
220uF
NC
CR9
16
JP1
J8-39
BLOWER ON CMD
11
K3
K2
K1
J7
1N4001
K6
DS2E-S-DC12V
CR8
+12V
R41
16
E1
K5
DS2E-S-DC12V
R36
E8
51K
E2
11
TO RESISTOR 1
E7
EMERGENCY
INTERLOCK
+12V
13
DS5
ON CMD
TO BLOWER
20K
DS9
13
T92S11A12-240
T92S11A12-240
1N4001
51K
THERMAL 2 FAIL
T92S11A12-240
R2
+12V
DS2
SCR 1 OPEN
K4
DS2E-S-DC12V
RES 2
THERMAL
J14
CR7
1N4001
51K
DS1
RES 1
THERMAL
J16
C12
AM2-A9A8AW
CB3
NO
13
AM2-A9A8AW
CB1
NO
16
AM2-A9A8AW
CB2
NO
51K
51K
R33
1K
DS8
TO RESISTOR 2
K5-11
J8-40
R42
DS7
DS6
K8
R35
51K
22uF
+12V
C15
22uF
LM324
Q1
2N2222
4K7
1K
R57
43K
13
10
1K
C11
.1uF
+12V
+12V
R40
L2
10K
U6-2
ILQ1
12
R56
C16
22uF
13
1K
R58
43K
R15
1K
U1B
LM324
R13
1K
R14
1K
R52
1K
10K
R53
22uF
+12V
R38
11
10K
R55
16
L2
R39
10
43K
10M
+12V
L1
15
U6-1
ILQ1
C13
R50
1K
R11
1K
U1C
R47
14
+12V
R51
1K
10K
LM324
13
+12V
L1
R10
1K
R49
1K
R37
R12
R16
U1D
14
LM324
R54
Q2
2N2222
4K7
43K
1K
11
C14
10M
C5
.1uF
+12V
1N4001
CR11
U2-4
ILQ1
R3
1K
U1A
R4
12
R48
12K
11
11
1N4001
CR10
R5
+12V
R21
11
+12V
U2-3
ILQ1
+12V
+12V
20K
470R
U2-2
ILQ1
16
U2-1
ILQ1
J2
R20
R18
470R
R19
1K
CSD2425
CSD2425
J1
R17
1K
R6
14
R34
51K
15
K7
DS10
SCR 2 OPEN
20K
LARCAN
M8
-12V
M6
M3
+12V +5V
M9
+12V
R7
L3
L4
L5
M7
M5
M4
M1
+5V
C7
2K7
DS3
J3
.1uF
U3
R22
7K5
PS1 FAIL
R29
F2
J1-1
L1
J8
L2
J1-2
2K
-12V
J8-31
PS1 STATUS
F1
CR3
80SQ040
+12V
R23
MC34161
1K
CR2
10
11
12
13
14
15
L2
-12V
8K2
L7
CR1
80SQ040
+12V
R24
+5V
C8
2K7
DS4
F4
PS2 FAIL
.1uF
L1
U4
-12V
J9
L2
R31
2K
J8-32
PS2 STATUS
+12V
C2
10uF
80SQ040
CR5
R30
MC34161
1K
C3
80SQ040
10uF
+5V
R25
CR4
8K2
R27
R9
9K1
9K1
C1
10uF
80SQ040
C9
R26
1K
1K
.1uF
U5
MC34161
10
11
12
13
14
15
+12V
-12V
J10
J11
J12
L11
C10
C6
C4
330pF 330pF 330pF
+12V +5V
L12
L13
J5
10
11
12
13
14
15
10
11
12
13
14
15
-12V
L9
L6
L10
PS1 STATUS
PS2 STATUS
-12V
L15
J6
+5V
+5V
R32
F3
CR6
R8
L8
J4
+5V
7K5
+12V +5V
80SQ040
R28
TX ON CMD
+12V +5V
L16
BLOWER ON CMD
K5-11
L17
L14
LARCAN
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
TABLE OF CONTENTS
1.
2.
INTRODUCTION .............................................................................................................1
CIRCUIT DESCRIPTION..................................................................................................1
General...............................................................................................................................1
On/Off Control And Interlock Functions . ...............................................................................2
Metering Display Circuitry ...................................................................................................2
AGC And VSWR Protection .................................................................................................3
Interconnection With The Transmitter ...................................................................................4
Remote Control ..................................................................................................................4
3. TESTING AND TROUBLESHOOTING..............................................................................5
Metering switches ................................................................................................................5
Interlocks ............................................................................................................................6
Control................................................................................................................................6
Remote Status and Telemetry interface ................................................................................7
AGC Circuitry ......................................................................................................................7
4. PARTS LIST....................................................................... Error! Bookmark not defined.
1.
INTRODUCTION
The MX1000 control system is completely self contained on a hinged panel at the front of the
transmitter. From this panel, the user can turn the transmitter on and off, raise and lower the
output power, and monitor all critical parameters and status. The interface for remote control of
the transmitter is also provided from this panel.
The control system handles all the interlocking control, protects the transmitter against excessive
VSWR and displays power supply status. Meters are provided for monitoring output power,
reflected power, P/S currents and AGC voltage.
Figure 1 Front Panel
2.
CIRCUIT DESCRIPTION
GENERAL
The circuitry is generally divided into various functional sections. Each section performs different
functions and is typically shown on a separate sheet of the schematic. The circuit board used in
the MX1000 was designed for dual uses. On the MX1000, this board is configured to control a
single transmitter. In another configuration (internally referred to as Group-2), this board controls
dual PA/Power supply cabinets.
ON/O FF CONTROL A ND INTERLOCK F UNCTIONS (P AGE 1 OF T HE SCHEMATIC ).
The ON/OFF state of the transmitter is determined by the state of the latching relay K6. Note that
OFF switch S11 is connected such that it is always enabled (this is a built in safety feature of the
transmitter: pressing S11 at any time, even if the transmitter is in remote mode will latch K6 into
the OFF state). The ON switch S12 is only enabled when the LOCAL/REMOTE switch Sl0
(shown in LOCAL mode) is placed in the LOCAL position. If S10 is in REMOTE mode, the
remote inputs are enabled and can turn on and off the transmitter.
Interlock connections to the control board are on J2. The signals from the interlock circuitry in the
transmitter are opto-isolated (U21, U22 and U24A) for circuit protection. Interlocks include the
airflow in the cabinet and the air temperature in the exhaust duct as well as another 'External'
interlock that can be connected to patch panel or coax switch interlocking circuits. The outputs of
the opto-isolators are fed to AND gates U19B and U19C. If an interlock opens or fails in any way,
these gates will remove the drive from the base of transistors Ul 7A and B. These transistors
buffer the ON command from K6 to turn on the power supplies.
Interlock failure also latches the associated latching relay (K3, K4, K7, K8, or K9). These
relays remain latched until a reset command is issued. If an interlock is opened and then
restored, the latching relay remains latched. This ensures that a "history" or record of the
interlock failure is retained. On early versions of the transmitter, this would cause the interlock
LED to remain off until the reset was given. Later versions of the control circuit included a circuit
that would cause the LEDs to blink on and off after the interlock was restored but before the reset
was pressed. A blinking LED indicates that the interlock was opened but subsequently restored.
Note that the command to turn on the blower is sent directly from relay K6 and is not included in
the interlock circuitry.
METERING DISPLAY CIRCUITRY (P AGE 2 A ND 3 O F T HE SCHEMATIC)
The circuitry shown on pages 2 and 3 of the schematic is identical in function. The two sets of
circuitry simply drive different meters. The metering circuit on the control board serves to route
the selected signal (coming from various points within the transmitter) to the front panel display
meter. As both metering circuits are the same, only the circuitry on page 2 of the schematic will
be described.
A debounce IC is used as a latching circuit for the meter selection switches. The debounce ICs
U6 and U7 (MC14490) use an oscillator to debounce the switch inputs. Capacitor C31 is
connected between to pins 7 and 9 of U7 and determines the frequency of oscillation. Buffer
inverter U42A is used to connect the oscillator output of U7 to pin 7 of U6. When a switch is
pressed, R33 is temporarily removed from the circuit allowing the oscillator to oscillate and the
debounce IC debounces the switch inputs. When the switch is released, R33 is grounded,
causing the oscillations to stop. At the point the oscillation is stopped, the output of the debounce
IC latches. The outputs remain latched in the last known state until the debounce oscillator is
functioning (user presses a selector switch). The outputs of U6 and U7 drive the selector inputs
of CMOS analog switch ICs U3 and U4. The output of these analog switches drive the digital
panel meter via buffer amplifier U9C and calibration pot R217.
The schematic shown on page 3 is identical in design to that of page 2, except for the obvious
component designation changes and that the buffer amplifier output drives the analog power
meter. This meter is current driven, so the adjustment pot R219 adjusts the current being fed
through the meter, as opposed to the voltage being fed to the meter.
AGC A ND VSWR PROTECTION (P AGE 4 OF T HE SCHEMATIC).
The AGC circuitry is designed to maintain the power of the transmitter at a particular power level,
however the AGC circuit is also used to generate cutback protection in the event of excessive
output VSWR.
Output power is sampled and detected by the RF detector board and fed to the AGC circuitry J8.
U35A buffers the voltage and feeds the metering display circuitry through calibration pot R164.
U35B is configured as a comparator, using the voltage from NOVPOT U43 as a reference voltage
against the sampled output voltage. The output of U35B feeds the AGC output via buffer
amplifier U35C. AGC enable switch S23 is shown in the "disable" position. In this position, the
AGC voltage is grounded through forward biased transistor U33D, thus disabling the ACG part of
the circuit.
U43 is a solid state Non Volatile Digital
Potentiometer. The IC has an internal pulse
counter and internal switching logic and the solid
state equivalent of a stepping motor to connect the
taps in an internal string of resistors, one at a time
to its "wiper" terminal. Programmable non-volatile
memory is provided within the device to maintain
its last setting and restore that setting during
power-up. U41 is configured as a clock pulse
generator providing the required clock signal to
U43. VR1 is a safety device that disables the
raise/lower circuitry from operation during power
fail or power-up conditions. This prevents
inadvertent transmitter power changes. The
output of VR1 feeds AND gate U38A. Pressing
the RAISE (S20) or LOWER (S17) switch causes
the other input to U38A to go high. This has the
effect of starting the clock generator, U41, and
placing a low on pin 7 of U43. If the RAISE switch
was pressed, pin 2 of U43 is low as well, causing
the "wiper" pin (pin5) of U43 to rise in voltage. If
the LOWER switch was pressed, pin2 of U43
stays low, causing pin 5 of U43 to lower in voltage.
AGC SYSTEM OPERATION
The function of the Automatic Gain
Control system is to keep the transmitter
operating at 100% over varying
environmental conditions. The intent of
this system is not to compensate for
device failures, or excessive loss in
output systems due to mismatch or poor
tuning. Power FETs have some
inherent change in gain over operating
temperature and this is the reason for
the AGC system. Generally, the AGC is
set up with 10 - 15% headroom.
Typically, this is done by disabling AGC,
setting the exciter for a tx output power
of 115%, then, with the AGC enabled,
lowering (or raising) the power for a
nominal 100% output. Of course, this
can only be done (properly) with a
healthy transmitter, at normal operating
temperature. The AGC control sends a
voltage to a variable attenuator located
in the 4-way splitter module. This
voltage is varied, depending on the gain
of the PA modules, to keep the
transmitter output constant.
The detected sample of the reflected power is fed
to comparator U29B. This signal is compared to a
factory set threshold level determined by resistor combination R142, R146,R138 and R125. As
the reflected power increases to this preset level, the output voltage from U29B will increase.
The output of U29B feeds buffer amplifier U35C and thus overrides the AGC voltage, causing the
transmitter power to drop. In addition, op-amp U29C compares the output voltage from U29B to
a factory preset level as determined by R137/R13O. As the output of U29B increases due to
VSWR, U29C will turn on the CUTBACK LED D56 on the front panel display.
The forward power telemetry is also sent to op-amp U28B where it is amplified by a factor of two
and then passed through a pot. The output from the pot is then sent to op-amp U28C. However,
if the output of the pot is too low, diode CR28 will pass a voltage of approximately 2.7V to the
input of the diode. The other input of op-amp U28C receives the reflected power telemetry. Now,
when pot R128 is set properly, if the reflected power telemetry reaches the same voltage as the
forward telemetry from pot R128, then you have high VSWR and the transmitter should be shut
off. The transmitter will be shut off because the output of op-amp U28C will cause relay K11 to
trip. When K11 trips, it sends a "VSWR OUT TRIP" indication to and gate U19A which causes
the transmitter to turn off. It will also cause K10 to trip, and stay tripped until a reset command is
issued, causing the VSWR trip led to record the VSWR trip. Now, once K11 trips, the input
capacitor to U31 A will start to charge. When it passes +5V, relay K11 will be set back to it's
original state and the transmitter will turn on again. In this way, a momentary VSWR will cause
the transmitter to trip off and then restart. However, each time relay K11 trips, the monostable IC
U30B sends a pulse to slightly charge capacitor C92. If the transmitter trips 3 times in
succession, capacitor C92 will have charged past the voltage present on the negative input of
U31B, which is provided by the voltage divider of R150 and R154. Should this happen, op-amp
U31B will cause relay K5 to trip. This will turn off the transmitter until a reset command is issued.
INTERCONNECTION W ITH T HE T RANSMITTER (P AGE 5 O F T HE SCHEMATIC)
Information from the various modules within the transmitter are fed to the control board via J3.
Table 1 details the signals and pins.
11
12
13
16
18
19
20
23
25
26
27
Table 1
Reset Command
Over Current Status
Current Telemetry
Over Voltage Status
Lockout Status
Over Current Status
Current Telemetry
Over Voltage Status
Lockout Status
Over Current Status
Current Telemetry
Over Voltage Status
Lockout Status
Over Current Status
Current Telemetry
Over Voltage Status
Lockout Status
All Regulators
Regulator 1
Regulator 1
Regulator 1
Regulator 1
Regulator 2
Regulator 2
Regulator 2
Regulator 2
Regulator 3
Regulator 3
Regulator 3
Regulator 3
Regulator 4
Regulator 4
Regulator 4
Regulator 4
The lockout information from the regulators is an open collector signal, these signals are bused
together to a “collective” lockout indication. The trip information is connected together in a similar
manner. Diode CR32 connects the trip and the lockout lines so that either a trip or a lockout of
the regulators will cause opto U31A to turn on U16B, causing the REGULATORS OK LED to turn
off. In addition, relay K1 will latch, causing the REGULATOR TRIP LED to turn on. K1 is also
connected to remote interface J5 which will indicate that a regulator tripped. If a regulator trips,
and then locks out, the REGULATORS OK LED will be off. However the REGULATOR TRIP
LED will blink, indicating the lockout. U8 is configured as an oscillator that controls the ‘blinking’
of the LEDs The clock signal from U8-3 passes through U5A only if a regulator has locked out.
This signal then alternately turns U16A on and off.
The current telemetry signals from the regulators are used for front panel metering and also
telemetry. These voltages pass through calibration pots R221, R225, R229 and R233. From
here they are buffered by op amp U2 and sent to both the remote control interface and to the
analog switches that send the signals to the meters.
Note: In the case of parallel 1kW cabinets, the information from the second amplifier cabinet is
returned to the control board via J4.Pl
R EMOTE CONTROL (P AGE 6 OF THE SCHEMATIC)
This page illustrates the routing of the remote control interface. Connector J11 is a 25 pin D-shell
connector that comprises the majority of the remote control interface connection. Remote control
connections are detailed in Table 2. When the front panel REMOTE switch is pressed, a remote
arming voltage is present and the grounding of a remote control input will result in that command
being issued. A remote reset command on J11-5 will cause the opto U24 to send a reset
command. This reset is split into an active low and an active high reset by transistors U20 B and
D.
Connectors J12, J13, J14, and J15 bring information from the PA's to the remote interface. On
those connectors pin 3 brings the cutback voltage, and pin 5 brings a RF OK indication. The
cutback voltage is buffered by op amps U10A, B ,C,D while the RF OK indication is isolated by
opto isolators U11A, U11B, U12A, U12B.
Table 2
Pin
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
3.
Signal
PA 1 Current
PA 2 Current
PA 3 Current
PA 4 Current
Reset
ON
OFF
AGC Raise
PA 1 Cutback
PA 2 Cutback
PA 3 Cutback
PA 4 Cutback
Reflected Power
Vis. Fwd. Power
Aur. Fwd. Power
AGC Lower
PA 1 RF OK
PA 2 RF OK
PA 3 RF OK
PA 4 RF OK
Ext Interlock
Temperature Interlock
Air Flow Interlock
Cab. 2 Temp. Interlock**
Cab. 2 Air Flow Interlock**
Function
Telemetry
Telemetry
Telemetry
Telemetry
Command
Command
Command
Command
Telemetry
Telemetry
Telemetry
Telemetry
Telemetry
Telemetry
Telemetry
Command
Status
Status
Status
Status
Status
Status
Status
Status
Status
TESTING AND TROUBLESHOOTING
For the most part, there is very little servicing that can be done to this circuit in the field. The
circuitry uses surface mount technology (SMT) and can be very difficult to service with
conventional tools. There are adjustments that are preset at the factory and do not require
readjustment under normal circumstances in the field. The following tests are in essence,
functional tests that can be performed to determine it the circuitry is indeed working properly. In
the event that the circuitry is not functioning the way it should, it is suggested that firstly, a visual
inspection be done for obvious problems, secondly, that wiring into and from the circuit board be
inspected and finally, that the circuit board be removed and replaced. For these tests, if the
board functionality is tested in the transmitter, it is recommended that the breakers for the blower,
and power supplies be left off.
•
METERING SWITCHES
Ensure that JP1 and JP2 are installed. Note: on the MX1000 version of this board, some
switches are not installed. These are for the dual cabinet version of the controller.
•
•
•
•
•
•
•
•
•
•
•
On power-up the LEDs on the VIS switch for POWER METERING should be lit as should the
LED on the PA1 switch for METERING.
When a switch button is pressed the corresponding LED should illuminate.
Select the VIS metering function on the POWER METERING section. Connect a variable
power supply set to 4 volts to J8-9. Adjust R164 for a reading of 100% on the power meter.
R219 may need adjustment in order to get the correct deflection on the meter.
Select the RFL metering function. Using the variable supply, apply 4 volts to J8-6. Adjust
R117 for a reading of 100% on the meter.
Select the AUR metering function. Connect the variable supply to J8-11. Note that the board
has no adjustment for the meter deflection in this function. In the transmitter calibration of
this function is done on the RF detector board. There should be meter to deflection for 4 volts
input.
Select the AGC metering function. Press the OFF switch. Measure the voltage on the BNC
connector J16. Adjust R217 so that the voltage measured at the BNC connector appears on
the LCD display (±0.1 volts).
Select the PA1 metering function. Apply a voltage between 1 and 2 volts to J3-4 and verify
that there is a meter reading. Note: a voltage higher than 2 volts will cause a reading of “1”
on the screen indicating an over-range condition.
Select the PA2 metering function. Apply a voltage between 1 and 2 volts to J3-4 and verify
that there is a meter reading.
Select the PA3 metering function. Apply a voltage between 1 and 2 volts to J3-4 and verify
that there is a meter reading.
Select the PA4 metering function. Apply a voltage between 1 and 2 volts to J3-4 and verify
that there is a meter reading.
INTERLOCKS
Install jumpers across:
J2-1 and J2-2
J2-3 and J2-4
J2-5 and J2-6
•
•
•
•
•
Press the reset button. The EXTERNAL, TEMP, and AIR LEDs should all be illuminated.
Remove the jumper across J2-1/J2-2. The EXTERNAL LED should extinguish. Re-install
the jumper. The LED should stay off until RESET is pressed. While the Led is on you should
see ground on J11-21, while the led is off, J11-21 will be floating.
Remove the jumper across J2-3 and J2-4. The TEMP led should turn off. Re-install that
jumper. The Led should stay off until you press reset. While the Led is on you should see
ground on J11-22, while the led is off, J11-22 will be floating.
Remove the jumper across J2-5 and J2-6. The AIR led should turn off. Re-install that
jumper. The Led should stay off until you press reset. While the Led is on you should see
ground on J11-23, while the led is off, J11-23 will be floating.
Again remove the jumper across J2-5 and J2-6. The AIR led should turn off. Re-install the
jumper. Put the board in remote (push in the remote button so the led on the switch is turned
on) and by grounding J11-5 you should be able to turn on the LED again.
CONTROL
In Remote mode, the local ON button (on the tx front panel) will not work. The OFF button will
still work. This is a built-in safety feature of the transmitter.
•
•
Verify that the REMOTE switch is in the Local, or ‘out’ position. The corresponding LED
should be off. The transmitter controller is in ‘Local’ control mode.
Press the ON switch and verify that its corresponding LED is illuminated. Press the OFF
switch and verify that its LED is illuminated and the ON LED is extinguished.
•
•
•
•
•
•
•
•
Press the REMOTE switch to set the control into ‘Remote’ mode. The LED on the REMOTE
switch should be illuminated. Press the OFF switch. The OFF LED will illuminate. Verify that
when the ON switch is pressed, there is no change in state.
Set the control back to ‘remote’ mode.
Ground J11-7, and verify that the OFF LED turns on.
Ground J11-6 and verify that the ON LED turns on and the OFF LED is extinguished.
Verify that with the control in ‘local’ mode that the above two steps have no effect on the
transmitter on/off state.
Press RESET. Verify that the REG OK LED is illuminated and the REG TRIP LED is
extinguished.
Verify that by grounding J3-2 (or any one of J3 pins 2,5,9,12,16,19,23,26), the REG TRIP
LED illuminates and REG OK LED turns off. The REG TRIP LED will only turn off when
RESET is pressed and there is no ground on J3-2 any of the other pins noted above.
Ground J3-6 (lockout). The REG TRIP LED should now blink. The LED will blink as long as
J3-6 is grounded (Any one of J3 pins 6, 13, 20, 27).
R EMOTE STATUS AND T ELEMETRY INTERFACE
•
Using a variable power supply set at approximately 4 volts, the voltage applied at pins listed
in the first column will be buffered and appear at the pin on the second column.
J12-2
J11-9
J13-2
J11-10
J14-2
J11-11
J15-2
J11-12
•
Grounding the pin listed in the first column, will result in a grounded pin in the second column
J12-5
J11-17
J13-5
J11-18
J14-5
J11-19
J15-5
J11-20
Apply a voltage (~4 volts) to J8-11. The same voltage should appear at J11-15.
Apply a voltage to J8-9. Adjust R164 for the same reading at J11-14.
Apply a voltage to J8-6. Adjust R117 so for the same reading at J11-13.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
AGC CIRCUITRY
Install jumpers across J2-7,8 and across J2-9,10.
Press the ON switch.
Apply +5V to J8-9. Do not apply any voltage to any other pins on that connector.
Push the ACG ENABLE switch. The LED on the switch should illuminate indicating AGC
control is enabled.
Measure the voltage on the AGC connector J16.
With the transmitter in local control mode, alternately pressing the AGC RAISE and LOWER
buttons you should be able to lower and raise the voltage on J16 (note: RAISE will actually
decrease the voltage and vice versa).
Set the control to remote mode. The AGC RAISE and LOWER switches will no longer vary
the voltage on J16. By alternately grounding pins J11-8 and J11-16 you should be able to
lower and raise the voltage on connector J16 (remotely).
Press the OFF switch.
The voltage on J16 should be substantially higher (approximately 8 volts or higher).
Press the ON switch.
Remove the voltage on J8-9. Apply +5V to J8-6.
Monitor the voltage at J16. Adjust R138 for approximately 1 volt at J16.
•
•
•
•
•
Adjust R137 and verify that DS6 can be turned on and off by this adjustment.
Apply +4V to J8-9. Adjust R128 for 4.0 Volts at U28-9.
Apply +4V to J8-6. The VSWR TRIP LED should illuminate and the VSWR L/O LED will
illuminate after a few seconds.
Remove the voltage from J8-6. Press RESET to clear the VSWR TRIP and VSWR L/O
LEDs.
Briefly touching +4V to J8-6 and removing it 3 times within a few seconds will cause
theVSWR L/O LED to come on and stay on until RESET is pressed.
VSWR OUT TRIP
(SH.4)
LOCAL/REMOTE 6
S10
R62
1K
MMPQ2222A
TQ2SA-L2-12V
U17D
HSMS-2800
CR22
HSMS-2800
16
14
R107 330pF
C84
1K
U26A
MOCD207
R105
1K5
DS9
U15B
MOCD207
+12V
J11-23
Cab 1 Air Ok
(SH.6)
CR20
HSMS-2800
J11-24
Cab 2 Temp Ok
(SH.6)
U26B
MOCD207
R101
1K5
R104 330pF
C82
1K
1K5
R103
CAB 2 TEMP
REMOTE ON CMD
J11-6
(SH.6)
CR19
HSMS-2800
DS8
R56
C53
R102
330pF
+12V
TQ2SA-L2-12V
K7
10
+12V
REMOTE OFF CMD
J11-7
(SH.6)
DS2
R71
1K
1K5
CAB 1 AIR
TQ2SA-L2-12V
K8
+12V
10
1K
U15A
MOCD207
+12V
CR10
R106
+12V
16
DS1
11
DS10
J11-22
Cab 1 Temp Ok
(SH.6)
CR21
HSMS-2800
R65
1K
C63
330pF
TRIP BLINKER
S11
U16-7 SH.5
1K5
R100
1K5
CR17
HSMS-2800
+12V
CAB 2 AIR
CR18
HSMS-2800
DS7
R99
U17C
10
6 CR9
HSMS-2800
+12V
R120 330pF
C90
1K
+12V
OFF
J4-37
CAB B ON CMD
(SH.5)
J11-21
Ext Ok
(SH.6)
330pF
U27B
MOCD207
R108
1K5
2K
K6
+12V
10
CAB 1 TEMP
R79
DS11
C85
CR12
HSMS-2800
TQ2SA-L2-12V
K9
+12V
10
U17B
C76
.01uF
S12
MMPQ2222A
12
R110
1K5
1K
U27A
MOCD207
100
+12V
100
R95
11
13
REMOTE ARM
(SH.4)
+12V
+12V
+5V 10
BLOWER ON CMD
J3-39
(SH.5) J4-39
2K
R113
DA
DB
O1
O2
O3
O4
O5
O6
15
+12V
I1
I2
I3
I4
I5
I6
GND
10
12
14
R91
R76
+12V
+12V
R96
10K
ON
LOCAL ARM
(SH.4)
EXT
16
13
10K
U23
10
2K
1K5
1K5
10
14073
REMOTE ARM
(SH.4)
R109
CR11
HSMS-2800
R114
MMPQ2222A
R77
U20A
MMPQ2222A
U17A
U19C
15
15
10K
14503
10
R88
+12V
330pF
R87
1uF
CR16
HSMS-2800
4K7
MMPQ2222A
11
12
13
U24A
MOCD207
1K5
+ C71
C73
.01uF
+12V
C81
+12V
+12V
TQ2SA-L2-12V
K3
+12V
10
100
14073
R92
10K
R98
CR15
HSMS-2800
DS12
VSWR
LOCKOUT
CR14
HSMS-2800
J3-37
CAB A ON CMD
(SH.5)
330pF
+12V
V LOCK
(SH.4)
100
R84
1K5
100
R82
11
13
O1
O2
O3
O4
O5
O6
C80
R111
1K5
+12V
R83
U19B
U22B
MOCD207
R97
330pF
Active High Reset
(SH.4)
RESET SW
J3-1
J4-1
(SH.5)
TQ2SA-L2-12V
K5
10
330pF
+12V
C83
CR13
HSMS-2800
DA
DB
R90
10K
+12V
L1
TQ2SA-L2-12V
K4
10
+12V
15
1K5
1uF
GND
I1
I2
I3
I4
I5
I6
+12V
10
12
14
U22A
MOCD207
R93
C79
RESET
+12V
C68
1uF
R81
14503
10
16
+12V
EXT
CAB 1
TEMP
CAB 1
AIR
CAB 2
TEMP
CAB 2
AIR
U18
R89
10K
+12V
+12V
+12V
330pF
J2
14073
R36
4K7
U21B
MOCD207
1K5
C86
+12V
R94
C77
14
R85
10K
+12V
U19A
1K5
330pF
+5V
C74 .01uF
U21A
MOCD207
R86
C75
R259
10K
Active Low Reset
SH.4 & 5 )
10
1K
+12V
+12V
+12V
R213
S13
330pF
C78
1K
U25A
MOCD207
J11-25
Cab 2 Air Ok
(SH.6)
+12V
+12V
+12V
TQ2SA-L2-12V
+12V
R39
R244
4K7
1K
Q5
MSD601
R34
R245
4K7
1K
Q6
MSD601
+5V
Ain
Bin
Cin
Din
Ein
S4
10
S2
PA4
10
S9
AGC V
10
S7
PA5
10
S5
PA6
10
10
R33
C31
1K
1000pF
1K
Q8
MSD601
R19
R246
4K7
1K
Q7
MSD601
R11
R248
4K7
1K
Q9
MSD601
JP1
14
+5V
10
R29
1K
R27
1K
R23
10 +
9 -
LM324
U9C
C93
1K
.1uF
R217
1K
+12V
+12V
Ain
Bin
Cin
Din
Ein
Aout
Bout
Cout
Dout
Eout
15
13
11
OsciIn OscOut
+5V
U42A
74HC04AD
+5V
S3
PA7
+12V
S1
PA8
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
1E
2E HC4066
3E
4E
10
R24
1K
R28
1K
R32
1K
R31
1K
MC14490
11
13
12
.01uF
U4
14
(SH.5)
+5V
C29 .01uF
14
12
330pF
C96
+5V
U6
+5V
1K
R22
C26
4K7
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
1E
2E
3E HC4066
4E
J9
14
R247
GND
OsciIn OscOut
+5V
R25
11
13
12
+12V
Select 1
(SH.3)
MC14490
PA3
+12V
Aout
Bout
Cout
Dout
Eout
15
13
11
.01uF
U3
11
14
12
PA1 I
U7
PA3 I
PA2
PA2 I
S6
(SH.5)
PA4 I
11
11
+5V
+5V
4K7
1K
Q4
MSD601
C30 .01uF
C20
GND
R12
R243
22uF
+5V
C34
+5V
PA1
10
10
+5V
2K
PA5 I
4K7
470
Q3
MSD601
PA6 I
PA7 I
R242
CR5
HSMS-2800
S8
R37
100K
R38
PA8 I
R20
LM324
U9A
16
4K7
470
Q2
MSD601
+5V
+12V
+12V
16
R241
22uF
+5V
R26
+ C33
HSMS-2800
1K
Q1
MSD601
2K +5V
GND
4K7
R240
10
CR6
GND
R35
10
R42
K2
R43
51K
U9B
LM324
Select Out
(SH.3)
+12V
+12V
R156
51K
R151
1K
Q14
MSD601
R192
R254
4K7
1K
Q15
MSD601
S18
OVERALL AURAL
10
S25
CAB 1 VIS
10
S22
CAB 1 REFL
10
14
12
Ain
Bin
Cin
Din
Ein
OsciIn OscOut
10
R149
1K
Q16
10
10
MSD601
R255
4K7
R158
1K
Q18
MSD601
R257
4K7
14
12
S24
CAB 1 AUR
R199
U36
9 -
U32C
LM324
+12V
1K
R195
C105
11
13
12
Ain
Bin
Cin
Din
Ein
Aout
Bout
Cout
Dout
Eout
15
13
11
.01uF
U44
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
1E
2E HC4066
3E
4E
OsciIn OscOut
C103
1000pF
U42B
AGC V
(SH.4)
74HC04AD
10
R206
1K
R207
1K
R211
1K
R204
1K
C97
+5V
S15
CAB 2 AUR
1K
R196
10 +
1K
MC14490
S14
CAB 2 REFL
14
GND
+5V
(SH.4)
VIS FWD (SH.4)
VIS RFL
J8-11
CMB AUR (SH.4)
+5V
C99 .01uF
S19
CAB 2 VIS
1K
R194
10
11
J7
10
11
10
11
10
11
+12V
4K7
1K
Q17
MSD601
R189
+5V
14
R171
15
13
11
MC14490
1K
R256
16
Aout
Bout
Cout
Dout
Eout
10
11
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
1E
2E
3E HC4066
4E
R219
50K
14
11
13
12
+12V
TXA VIS
10
U39
.01uF
U37
+5V
4K7
S16
OVERALL RFL
+5V
330pF
C101
Select 1
(SH.2)
11
13
12
.01uF
U34
+5V
14
R253
+5V
C102 .01uF
C35
R218
50K
+5V
R181
OVERALL VISUAL
J10
C98
22uF
4K7
Q13
MSD601
GND
2K
+5V
R252
GND
R198
1K
TXA AUR
JP2
HSMS-2800
TXA RFL
4K7
1K
Q12
MSD601
10
S21
TXB AUR
CR30
TXB RFL
R177
R251
R159
+5V
4K7
1K
Q11
MSD601
LM324
U32B
16
R161
100K
+12V
TQ2SA-L2-12V
+5V
R250
+12V
GND
R167
C94
GND
1K
Q10
MSD601
10 HSMS-2800
4K7
22uF
R249
10
2K
+5V
TXB FWD
R185
11
K12
+5V
11
+12V
CR31
U32A
LM324
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
1E
2E HC4066
3E
4E
10
R172
1K
R173
1K
Select Out
(SH.2)
J6
+12V
TQ2SA-L2-12V
K10
10
VSWR TRIP
+12V
DS13
R112
2K
100K
5K
U29B
R139
10K
LM324
R132
R145
470K
U29D
12
R144
3K6
10K
U28B
LM324
CR28
HSMS-2800
10K
16
CR26
HSMS-2800
U30A
R152
4K7
13
U33B
MMPQ2222A
CX
RX/CX
14528
C89
+12V
12
11
10K
R178
U33D
R190
2K
R187
2K
U43
X9C103P
+12V
6 -
U31B
LM324
R150
3K
11
10K
U33C
R154
1K
12
Active High Reset
(SH.1)
CV
THR
U41
555
LOCAL ARM
(SH.1)
R179 10K 6
R183 1K 8
+5V
R208
AGC LOWER 2
R166 1K 6
MOCD207
U45B
DS14
R170 1K
R165
100K
10
REMOTE ARM
(SH.1)
R210
1K
R209
470
U46A
R193
4K7
L4
470
U45A
AGC RAISE
L2
S17
C109
.01uF
GND
GND
10K
S20
R176 1K 10
C107
330pF
REM AGC RAISE
J11-8
(SH. 6)
R201
10K
R175
6K8
R203
330
R184
VR2
6K8
MC34064
2 IN
OUT
2K
R191
DIS
2K
R197
100K
TR
10uF
OUT
14
+5V
GND
R186
74HC08
IN
+5V
+5V
U38A 14
+5V
J16
+12V
VR1
MC34064
U40A
74HC04AD
+5V
GND
R155
1K
R162
+5V
74HC04AD
22M
5 +
AGC
+5V
.01uF
R188
U40B
1K
+12V
10
MMPQ2222A
C114
C92
10uF
S23
C100 .22uF
510
510
C104
330pF
LM324
11
R148
1K
R182
LM324
470K
R205
10K
HSMS-2800
AGC OUT
R180
9 -
11
100K
+5V
CX
RX/CX
R153
R141
14528
U35C
10 +
U35B
6 -
C110
R134
MMPQ2222A 10uF
CR27
10
MMPQ2222A
R157
C95
330pF
+12V
R239
50K
+12V
5 +
470
1K C115
VIS FWD
(SH.3)
R164
10K
R160
FWD
HSMS-2800
4K7
+12V
U20C
13
15
14
CR34
HSMS-2800 R237
11
10
10K
CR33
R238
R168
10K
U35A
LM324
CAB A ON CMD
J3-37
12
11
R169
U30B
+12V
11
+12V
R236 1K
R202
2K
.1uF
CMB AUR
(SH.3 & 6)
R200
27K
R126
R122
100K
AGC V
(SH.3)
10K
(SH.1)
VSWR OUT TRIP 4
C87
.01uF
R128
10K
+12V
U33A
+12V
CR25
TQ2SA-L2-12V
K11
10
HSMS-2800
+12V
R143 1K
LM324
+12V
R136
1K5
+12V
R174
14
13 LM324
18K
R147
2K
R146
510
9 -
R129
15
4K7
R124
10K
C116
330pF
9 LM324
1K
R140
LM324
U28C
10 +
CR24
HSMS-2800
14
R116
100K R138
330pF
6 -
+12V
+5V
Active Low Reset
(SH.1)
MMPQ2222A
U31A
R125
11
C88
1K5
11
5 +
470
R258
100K
R115
RFL
+12V
2 -
C91
10uF
R127
5K1
+12V
R78
U29C
10
R131
VIS RFL
(SH.3)
R142
5K1
LM324
10
11
1K
R123
10K
11
R117
10K
+12V
J8
10
11
R130
2K
U29A
LM324
R118
2 -
R121
10K
+12V
3 +
DS6
CUT BACK
3 +
1K
CR29
HSMS-2800
16
R137
3K6
100K
U28A
11
R119
10K
R133
11
+12V
+12V
R135
+12V
+12V
CR23
HSMS-2800
MOCD207
DS15
R212
1K
REM AGC LOWER
C111
330pF
J11-16
(SH. 6)
V LOCK
(SH.1)
+12V
PA1 I
SH.2
R15
1K
R221
1K
3 +
2 U2A
C19
330pF
R14
1K
1K
C51
PA2 I
SH.2
330pF
R18
CR32
HSMS-2800
J3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
HSMS-2800
CR4
1K
330pF
5 +
6 -U2B
LM324
C24
330pF
R16
C18
R229
1K
1K
330pF
C21
330pF
R230
10 +
U2C
9 LM324
R231
C12
R233
1K
1K
330pF
C15
330pF
12 +
14
13 -U2D
LM324
HSMS-2800
PA5 I
SH.2
CR3
CR1
HSMS-2800
C6
R4
1K
330pF
PA6 I
SH.2
R8 1K
PA7 I
SH.2
C10
1K
330pF
R6 1K
330pF
BLOWER ON CMD
(SH.1)
LM324
R232
1K
R2 1K
330pF
6 -
LM324
I-PA4
C11
330pF
J11-4
(SH.6)
R3
430
C2
330pF
R7
430
C13
330pF
U1C
10 +
9 -
330pF
C5
C1
R9
430
U1B
5 +
330pF
PA8 I
SH.2
CAB A ON CMD
(SH.1)
330pF
2 -
330pF
DS3
U1A
3 +
C4
CONTROL
R80
1K
J11-3
(SH.6)
1K
+12V
1K
330pF
C8
C27
I-PA3
C23
330pF
R235
R234
C54
330pF
PS OK
R17
430
PA4 I
SH.2
R10
C14
C28 R30
R228
1K
1K
1K
R13
1K
J11-2
(SH.6)
PA3 I
SH.2
(SH.1)
+12V
U5A
MOCD207
C25
330pF
1K
1K
CAB B ON CMD
J3 & J4 LOCKOUT
I-PA2
430
R227
R226
C9
+12V
R21
HSMS-2800
CR2
C22
R225
1K
R224
1K
11
J4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
J11-1
(SH.6)
R223
R222
RESET SW
(SH.1)
I-PA1
C16
330pF
430
LM324
11
C17
330pF
R220
1K
LM324
R5
430
C7
330pF
U1D
12 +
14
13 -
LM324
J5
R1
430
330pF
330pF
C3
R63
15
U16A
16
4K7
+12V
MMPQ2222A
R59
R75
1K
C36
10uF
DS4
REG OK
REG TRIP
13
R68
R72
4K7
4K7
11
+12V
CR8
U13B
MOCD207
DS5
REG TRIP
555
MMPQ2222A
U16C
U8
U16B
MMPQ2222A
THR
TQ2SA-L2-12V
K1
CR7
10
HSMS-2800
+12V
C58
12
CV
R41
100K
U13A
MOCD207
330pF
HSMS-2800
L6
(SH.1)
Active Low Reset
+12V
R69
1K
L5
DIS
R40
1K
1K
BLOWER ON CMD
(SH.1)
14
GND
TR
C32
.01uF
+5V
+5V
L3
+12V
10
1K
U16D
MMPQ2222A
+12V
R67
TRIP BLINKER
R49
1K5
L7
C112
K3,K4,K7,K8,K9-4
SH.1
+5V
-12V
220uF
R48
1K5
C108 C106
220uF 22OuF
J1
C41
1K
330pF
13 -
LM324
430
C46
U12A
MOCD207
LM324
330pF
1K
11
C59
330pF
R45
430
C38
330pF
1K5
C64
330pF
C60
330pF
5 +
6 -
LM324
74HC08
10 +
9 -
1K5
C70
330pF
LM324
430
C67
330pF
1K5
C37
330pF
gnd
M7
gnd
14
14 7
gnd
M4
gnd
M1
M9
gnd
gnd
M6
M10
J15
U25B
MOCD207
M8
M5
gnd
10
11
12
13
14
15
13
74HC08
U5B
MOCD207
gnd
R47
330pF
R70
12
U46B
MOCD207
M2
U11A
MOCD207
C43
U14C
14
LM324
14
14
C48
330pF
+12V
74HC08
R74
430
U31D
14
U38D
R53
C44
U14B
LM324
13 -
7U38C
C72
330pF
330pF
U9D
13 -
10
U11B
MOCD207
R61
430
12 +
LM324
12 +
LM324
2 -
U14A
LM324
+12V
3 +
R66
C69
CMB AUR
J8-11 (SH.4)
R60
C61
330pF
330pF
330pF
U10D
14
9 -
+12V
330pF
1K
14
13 -
U38B 14
R52
C66
1K
VIS FWD (SH.4)
R73
C65
U14D
+12V
VIS RFL (SH.4)
R64
C62
12 +
12 +
14
13 -
U10C
11
J14
C52
330pF
330pF
330pF
10
11
12
13
14
15
330pF
C57
330pF
LM324
U32D
R50
C40
1K5
LM324
U31C
10 +
430
LM324
C50
R54
12 +
R58
U28D
14
13 -
LM324
74HC04AD
gnd
M3
gnd
330pF
9 -
330pF
10 +
U12B
MOCD207
U10B
12 +
14
12
74HC04AD
C49
1K
6 -
C39
330pF
430
U35D
U42F
13
330pF
5 +
74HC04AD
11
C47
1K
330pF
C56
J13
LM324
+12V
R55
C55
R57
10
11
12
13
14
15
2 -
13 -
330pF
R46
330pF
C45
1K
12 +
U10A
C42
3 +
R51
11
J12
10
11
12
13
14
15
10
11
REM AGC RAISE
U42E
11
MMPQ2222A
74HC04AD
SH.4 REM AGC LOWER
+12V
U42D
11
Ext Ok
SH.1 REMOTE OFF CMD
SH.4
U42C
Cab 1 Temp Ok
U40F
11
SH.1 REMOTE ON CMD
4K7
SH.1
Cab 1 Air Ok
U40E
Cab 2 Temp Ok
U40D
74HC04AD
12
11
J11-4
74HC04AD
10
13
14 7
U40C
Cab 2 Air Ok
J11-5
R216
74HC04AD
11
14 7
J11-3
74HC04AD
SH.5 I-PA3
SH.5 I-PA4
J11-2
11
C113
J11-1
SH.5 I-PA2
R215
1K
330pF
13
U20B
14
Active Low Reset
SH.1
10
4K7
Active High Reset
DS16
R214
U20D
SH.5 I-PA1
14 7
U24B
MOCD207
MMPQ2222A
14
14
+5V REMOTE ARM
SH.1
+5V
14
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
J11
11
TABLE OF CONTENTS
1.
2.
INTRODUCTION .............................................................................................................1
OUTPUT ALIGNMENT.....................................................................................................1
Required Equipment: ...........................................................................................................1
Procedure...........................................................................................................................1
3. OUTPUT CHANNELING INFORMATION ..........................................................................4
1.
INTRODUCTION
The bandpass filter is a three-pole filter, the center frequency of each pole being determined by
an adjustable line capable of being screwed into or out of the cavity. Two lines are available:
•
•
470-600 MHz range; and
600-800 MHz range.
The input and output coupling are controlled by the area of variable loops in the cavities. As
these are pushed further into the cavity, the effective area increases, resulting in more magnetic
lines within the cavity being intercepted and thereby tighter coupling. The intercavity coupling is
controlled by the depth of the capacitive probes within each cavity
The use of both capacitive and magnetic coupling results in a bandpass that is symmetrical in
off-channel rejection. The bandpass filter is normally aligned to be slightly overcoupled. This
results in a suppression of the out-of-band ±4.5 MHz products of approximately 14 dB. The
overall insertion loss of this section is approximat ely 0.5 dB.
2.
OUTPUT ALIGNMENT
R EQUIRED EQUIPMENT :
The following test equipment is required to align the output of the XLS1000 transmitter:
• 0-1,000 MHz Sweep Generator (Wavetek 1080 or equivalent);
• X-Y Oscilloscope (Hitachi V-212 or equivalent);
• 50 Ω detector (TTC 8520-301 or equivalent);
• Wiltron return loss bridge 62NF50;
• 7/8"-N adaptor (Andrew 2260B or equivalent);
• HN female-t o-N female adaptor;
• 50 Ω load (Microlab TA6MN or equivalent);
• 50 Ω coaxial cables for connections.
Note that the first four Items can be replaced by an appropriate network analyzer and its
associated accessories.
PROCEDURE
Set the sweep generator to the channel of operation.
Sweep width should be adjusted to 2 MHz/division.
A reference-setting sweep should be sent directly into the detector set for seven divisions
of deflection on the scope.
4.
Connect the equipment as shown in Figure 1.
5.
Set L102, L104 and L106 for an approximate on-channel bandpass.
Note: During each of the following steps, fine tune these adjustments to maintain the best
possible bandpass.
1.
2.
3.
6.
Set L103 and L105 for minimum insertion loss.
7.
Flatten the response using L101 and L107.
8.
Set L201 and L202 for the out-of-band ± difference beats.
Note: Notch filters L201 and/or L202 may or may not be present. If both filters are present, try
each notch on both sides as one combination may have less adverse effects on the bandpass
than the other.
Figure 1. Sweep Alignment Test Set-up
9.
10.
Re-flatten the response using L101 and L102.
Set width of filter using L103 and L105. The width should be equal to the aural-to-visual
difference of +0.5 MHz (total of 5 MHz for NTSC in North America). Ideally, waveshape
should appear as shown in Figure 2.
Figure 2. Ideal NTSC Response
11.
12.
Adjusting L105 and L107 interactively with each other, tune for proper bandwidth and
best out-of-band rejection.
Adjusting L103 and L101 interactively with each other, tune for proper bandwidth and
best out-of-band rejection.
Figure 3. Return Loss Set-up
13.
14.
Configure the equipment for return loss measurements, as shown in Figure 3.
Return loss should be 30 dB at carriers (Reference Figure 4).
Figure 4. Ideal Return Loss
15.
Readjust the filter slightly as needed to obtain proper response.
Note: During this test, the Wavetek 1080 should be set to maximum output.
16. Reconnect the equipment as in Figure 1 and repeat the sweep setup to compare response to
the NTSC ideal in Figure 2.
17. If the response is acceptable (less than 0.8 dB loss), return to the return loss setup and lock
down all adjustments on the bandpass filter.
18. Notches should be locked down after performing the final fine adjustment with a television
signal.
3.
OUTPUT CHANNELING INFORMATION
BPF Lines 3 ea.
• 470-600 MHz Part Number 6920-6008
• 600-806 MHz Part Number 6920-6009
Notch Filter Line Discs 2 ea.
• 470-506 MHz Part Number 1314-2016-4
• 506-570 MHz Part Number 1314-2016-3
• 570-690 MHz Part Number 1314-2016-2
• 690-806 MHz No disks used

---

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