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M820-00 Mechanical A2.1

Copyright TEL 01/07/00

2 Mechanical

2.1 Torx Recess Head Screws

Torx recess head screws are becoming the standard screw head type in all T800 Series II

equipment, with Pozidriv and Philips recess head screws being used in fewer applica-

tions.

The Torx recess head has the advantage of improved screwdriver tip location, reducing

the chances of screw head damage caused by the driver tip rotating within the recess. In

addition, using a ball-tip Torx screwdriver allows you to drive a Torx head screw with

the driver on a slight angle, which can be useful in situations where access is restricted.

It is important that you use the correct Torx screwdriver tip:

M3 screws - T10

M4 screws - T20.

Figure 2.1 below shows a typical Torx recess head screw (actual hardware may differ

slightly from this illustration due to variations in manufacturing techniques).

Figure 2.1 Torx Screw Identification

"star" shaped recess with

six internal notches

A2.2 Mechanical M820-00

01/07/00 Copyright TEL

2.2 Pozidriv & Philips Recess Head Screws

Pozidriv and Philips recess head screws will continue to be used in T800 Series II equip-

ment in a few special applications. It is important that you use the correct type and size

screwdriver for each screw type to avoid damaging the screw head.

It is particularly important that you do not use Philips screwdrivers on Pozidriv screw

heads as the tapered driving flutes of the Philips screwdriver do not engage correctly

with the parallel-sided slots in the Pozidriv screw head. This can result in considerable

damage to the screw head if the screwdriver tip turns inside the recess.

Note: If you find you need excessive downwards pressure to keep the screwdriver

tip in the Pozidriv screw head, you are probably using the wrong type and/

or size screwdriver.

Figure 2.2 below shows the main differences between typical Pozidriv and Philips screw

heads and screwdriver tips (actual hardware may differ slightly from these illustrations

due to variations in manufacturing techniques).

Figure 2.2 Pozidriv & Philips Screw & Screwdriver Identification

driving flutes with

parallel sides

driving flutes with

tapered sides

Pozidriv Philips

internal notches

"star" markings

between slots

no special markings

slots with parallel sides

slots with tapered sides

ridges between

driving flutes

M820-00 Mechanical A2.3

Copyright TEL 01/07/00

2.3 Disassembly/Reassembly

2.3.1 Receivers/Exciters/Transmitters

To carry out alignment or change option links, you need to remove only the top cover,

i.e. the one adjacent to the front panel handle and on the opposite side to the main

D-range connector (D-range 1/PL100).

You need to remove the bottom cover to:

• access transmitter RF power transistors and many SMD components

• change solder blob links

• fit test leads to circuit block access points.

2.3.2 Power Amplifiers

You should carry out the tuning and power output level setting procedures with the

cover on.

2.4 Cover Screw Torques

Receivers/Exciters/Transmitters .. 1.36Nm/12in.lbf.

Power Amplifiers .. 0.9Nm/8in.lbf.

A2.4 Mechanical M820-00

01/07/00 Copyright TEL

2.5 Chassis & Cover Compatibility

The chassis and covers used in T800 Series II modules incorporate a number of design

changes to improve Electro-Magnetic Compatibility (EMC) performance. It is impor-

tant that only the new-design covers are fitted to the new chassis to ensure correct

mechanical fit and continued compliance with appropriate EMC Type Approval regula-

tions.

Figure 2.3 below shows some of the main features which can be used to identify the

new-design chassis and covers.

Figure 2.3 Identification Of New-Design Chassis & Covers

Top Cover

Bottom Cover

Chassis

4 holes in

rear panel

loom channel in

top of walls

groove in top

of rear wall

ridge on top

of rear wall

provision for mounting speaker

(future development)

additional walls

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