TM8100/TM8200 Service Manual Fault Finding of Control Head with 1- 2- or 3-Digit Display 435
© Tait Electronics Limited June 2006
15.5 Some but not All Keys Faulty
If one or more (but not all) of the keys are faulty, repair the control head as
follows:
1. Disconnect the control-head loom and remove the control-head
board.
2. Use isopropyl alcohol and a soft lens-cleaning cloth to clean the pads
on the control-head board for those keys that are faulty.
3. Re-install the control-head board.
4. Reconnect the control-head loom and test the keys. If the fault has
been removed, return to “Initial Tasks” on page 149. If it has not, go
to Step 5.
5. Replace the keypad.
6. Re-assemble the control head. Reconnect the control-head loom,
test the keys to confirm the removal of the fault, and return to “Initial
Tasks” on page 149.
15.6 All Keys Faulty
If all the keys, with the exception of the ON/OFF key, are faulty:
1. Disconnect the control-head loom. Replace IC4, which reads the
status of the keys. See Figure 15.2.
2. Reconnect the control-head loom and test the keys to confirm the
removal of the fault. If the fault has been removed, return to “Initial
Tasks” on page 149. If it has not, replace the control-head board and
return to “Initial Tasks” on page 149.
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