TM8100 Mobile Radio Service Manual Servicing of Control Head 157
May 2004 © Tait Electronics Limited
Tas k 5 —
Volume Control Faulty
If the volume control works only intermittently, works only at full
volume, or does not work at all, repair the control head as follows:
1. Disconnect the control-head loom.
2. Check that the resistance between pins 1 and 2 of the volume-
control potentiometer RV1 [at 1D3] varies linearly between about
0 Ω and 10 kΩ. (see Figure 7.2). If it does, go to Step 3. If it does
not, go to Step 6.
3. Disassemble the control head completely as described in
Subsection 6.2 (on page 131).
4. Replace the speaker with a spare. Obtain a spare speaker by
disassembling the spare control head of Spares kit 1 or 10 as
described in Subsection 6.2.
5. Re-assemble the control head as described in Subsection 6.5
(on page 148). Reconnect the control-head loom. Confirm the
removal of the fault, and return to Subsection 5.2 (on page 109).
6. Remove the control-head board as described in Subsection 6.2.
7. Replace the potentiometer RV1. See Figure 7.1.
8. Re-install the control-head board as described in Subsection 6.5.
Reconnect the control-head loom. Confirm the removal of the
fault, and return to Subsection 5.2.
7.2 Faults Involving Control-head Board
Types of Faults This subsection gives the procedure for repairing a faulty control-head
board. (Level-1 service centres should replace the board as described in
Subsection 7.4 (on page 163), rather than attempt to repair it.) A faulty
board can have the following effects:
■ display faulty but not LEDs
■ some LEDs faulty
■ all LEDs faulty
■ display and all LEDs faulty
■ all keys faulty
In the case of a faulty display, the cause will have been narrowed to the
board following the checks in Subsection 7.1 (on page 151). The repair
procedures are given below in Tasks 1 to 5 respectively. For obtaining
replacement components, refer to Subsection 7.3 (on page 160).
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