Tait TM8100 mobiles, Service Manual

Page: 453 / 620

TM8100/TM8200 Service Manual Fault Finding of Control Head with 1-, 2- or 3-Digit Display 453
© Tait Electronics Limited November 2007
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 155 . 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 155 .
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 155 . If it has not, replace the control-head board and
return to “Initial Tasks” on page 155 .