Spectra Engineering MX800AB Repeater/Base Station User Manual 6 TroubleShooting

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Document Description	Toubleshooting
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Date Submitted	2001-04-03 00:00:00
Date Available	2001-05-18 00:00:00
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Document Title	6_TroubleShooting.PDF
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Technical Manual
6. MX800 Base Station Fault
Finding Procedure
The following test equipment may be required for the following tests:
MXTOOLS (MXBOO Base Station Programing Utility)
MXTOOLS User Manual
RF Test Set (eg HP 8920 or equivalent)
CRO (Cathode Ray Oscilloscope)
RF Power Meter (capable of measuring in Watts)
Multimeter
oilsv DC Power Supply
Network Analyser
6.1 MX800 Base Station
(the touowing tests will ltelp diagnose faulty modules)
oooooooo
0 Check voltage supply to tlte stuo by measuring both sides of Fuse 1
located on the Microconltollet PCB. Replace fuse If necessary.
0 Chechhal the power LED is lit. If not then go to section 62,
0 Using MXTOOLS check that the frequency tables and configuration
settings are Correct Refer to the MXTOOLS User Manual.
6.1.1 Transmitter Section
0 Connect the output of the Power Amplifier Module to a oomms test set
or RF puwet meter.
0 Check (It: Exciter locking Voltage is between 2 — 18 V on the TX VCO
T? on the Mictoconlrnller PCB.
0 If the locking voltage is out of spec then go to section 6A
0 Key up tlte transmitter using tire software m in MXTOOLS or by
connecting pin 12 of the IS-way connector at the tear of the radio.
0 If the output power of the PA is low then check the RF level out of the
Exciter module.
0 tithe RF power out ottne Exciter module is less rlran +23 dBm
(200 mW), ttten go to section 6.4 else go to section 6.5.
0 inject a 1 kHz tone via the mxsno lest jig and check for 1.5 kHz /3 kHz
peak to peak demodulated deviation.
0 II the audio deviation is incorrecl then go to the Exciter Alignment
prmdute section 5.2.1.
e SPECTRA ENGINEERING 2000 Fievlston 4.01 51
anot) Transceiver Yechnical Manual
if there is no audio modulation then check the audio level on pin 13,
Icllon the Micmcuntruller PCBr
If there is no audio on the above test point then go to section 5.2 else go
to section 6.4
6.1.2 Receiver Section
6.2
6.3
6.3.1
Check the Rx locking voltage is between 2 — 18 V at the RX VCO TP on
the Micmcontroller PCB.
if the Rx locking voltage is out of spec then go to section 6.3.
Inject a —6{} dBm RF test signal set to CF and modulated with a 1kHz
15 kHz / 3 kHz tune into the receiver BNC input connector.
Check for an audio signal on the mxsoo test jig.
Inject the test signal directly into the RX module and re-test for an audio
signal on the mxsoo test jig.
Replace the Rx input coax cable if faulty.
Check for an audio signal on pin 5 of IC 41 on the Micrcoornroller PCB.
If there is no audio signal on the above test point then go to section 5.3
else go to section 6.2.
Microcontroller PCB
Check pin 21 of [Cl is Law When FIT is on. If OK, then Check the output at
pin 17 of IC7 is HIGH. If OIL then PA may be faulty, Go to section 6.5
Check all jumpers and switch settings ore in the correct position for you
requirements.
The Micmoontroller PCB requires specialized test software to chcolt all the
hardware input and output ports. Please return the Microcontrolier PCB the
your nearest Customer service Centre.
Receiver Module
VCO Locking.
Check the value of X3 (13 MHz or 14.4 MHz) is the s'ame as the Rx
Reference Freq in the ‘Hardware SettingsY in MXTOOLS’ configuration
menu.
Connect a DVM (digital voltmeter) to the Rx vco 11> and check the
Rx locking voltage is between 2 -1s v at the Rx vco T? on the
Microcontroller PCB.
If the Rx locking voltage is out of spec then slowly adjust crl on the
Rx vco a full 360", and check for a change in the locking voltage
if there is a change in the locking voltage then realign the vco voltage
to 9V at the centre frequency.
52
6 SPECTRA ENGINEERING 2000 Revision 4.01
Technical Manual Drawings
llthcre is no change in the RX vco locking voltage, then check lhal the
vco supply voltage at SKUas is greater than 7v and with a CRO check
the 1'ch is oscillating on pin 8 of [C10.
If all the above t=sts pass then the VCO or [Clo may be faulty. Return
the Receiver Module to your Service Centre.
5.3.2 RX Front End
Snlder a Z-way Berg header onto a flying coax lead. Remove solder link
I near the mixer (M1) and then fit solderlink l. Inject a RF signal into
CNS. Check the sensitivity is better than —110 dBm.
if the sensitivity is OK past this point, then check that the supply voltage
to Him is greater than 4.5 v, lt the supply is OK. then replaoelc12.lf
this does not repair the receiver then the alignment may be incorrect or
other components on the front end may be faulty. Return the Receiver
Module to youl nearest Culomer Service Centre,
6.3.3 IF Section
oo‘o
If the Receiver has low sensitivity past this point then increase the RF
level to —60 (IBM and check Ihe RX DISC voltage is set (0 2.55V. Adjnsl
1.14 if necessary.
Connect a max lead with a pickup loop around the end from the antenna
input on the uremia lo the case of Xl. Set the upsezo to 7x test.
change the Tune Mode to Manual and change the centre frequency of
the comms test set to 44.54SMHz for A to B Band and 89.545MHz for c
Band and above.
it Cl'l cannot be adjusted to match the abave frequencies then x1 may
be faulty.
Set the centre frequency of the HPBQZOA to the RX freq + 45MHz for A
to B band or RX freq + 90MHZ for C to 1 Band or RX freq — 90MHz for
K band and above.
Adjust the TCXO to within +/» 201-11. (Check that the vco deviation is
set to 127 using MXTOOLS when adjusting the local oscillator)
If the RX oentre frequency cannot be adjusted the TCXO may be faulty.
Adjust T1 and 12 for minimum distortion, less than 195,
if the distortion is high then FL3A, FLsB or FM may be faulty.
If the sensitivity is still had then return the Module In your Service
Centre.
6.4 Exciter Module
6.4.1 VCO Locking.
Check the reference frequency of X3 (13 MHz or 14,4 MHz) is the same
as the TX Reference Freq in the ‘Hardware Sellings’ in MxToms‘
mnfiguration menu.
c: SPECTRA ENGINEERING 2000 Revision 4,0' 53
Mxetm Transceiver Technical Manual
Connect a DVM to the TX VCO TP and check the TX locking vollage is
belween 2 — 18 V on the TX VCO T? on the Microconlroller PCB.
It the Tx locking vollage is out of spec then slowly adjust crl on the
TX vco a full 360°, and check for a change in the locking voltage.
If there is a change in locking voltage, then realign the VCO voltage to
9V at centre frequency.
if there is no change in the TX vco locking voltage then check the
vco supply voltage at SKU~3 is greater than 7v and with a CRO check
the TCXO is oscillating on pin ti one 10.
if all the above tests pass then the vco or 100 may be faulty. Return
the Receiver Module to your nearest Customer Service Centre,
6.4.2 RF Power
Check the output power is greater than +73 dBm.
If the Exciter power is low then check for the +8 V supply voltage at the
outputs of ICZ and TRA.
Use a RF probe Io check for gain through [Cl and m4.
Lift R2 and solder a flying lead to the junction ole and R2, check the
output power of the vet) is greater than 7 dBm.
If all the above tests pass, then return the Exciter Module to your nearest
Customer Service Centre.
6.5 Power Amplifier
First do a visual check of all the oornponents on the PA looking for any
damaged components
Check the output power of the Exciter Module is greater than +Z3dBm.
With m oft measure the +118 v supply at the collector of the output
llansisml,
Key up the PA and check the supply voltage on the hybrid module. Refer
to your circuit diagram for test points
Lift the RF output lead of the hybrid and solder a flying lead to the lifted
leg. Connect the earth of the flying lead to the earth of the PA.
Check that the output of the hybrid is greater than sw.
The hybrid may be faulty if it has an output of less than sw and the
output transistor may be faulty ifthe hybrid has an output power of
_ greater than sw.
54
62 SPECTRA ENGINEERlNG 2000 Heylslon 4.0!

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Title                           : 6_TroubleShooting.PDF
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