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432 Fault Finding of Control Head with 1- 2- or 3-Digit Display TM8100/TM8200 Service Manual

15.1 Display Faulty but not LEDs

Elastomeric Strips

Faulty

If all the LEDs function correctly but the display functions only partially or

not at all, first check the elastomeric strips:

1. Disconnect the control-head loom from the control head. Remove

the control-head board.

2. Remove the elastomeric strips and check the conductors in the strips

for continuity. Replace the strips if they are faulty.

3. Ensure that the conductors along the edges of the strips are clean.

Use isopropyl alcohol and a soft lens-cleaning cloth to clean the

edges.

4. Use isopropyl alcohol and a soft lens-cleaning cloth to clean the pads

for the LCD on the control-head board.

5. Insert the elastomeric strips in their slots in the space-frame.

6. Re-assemble the control-head board.

7. Reconnect the control-head loom to the control head and test the

user interface. If the fault has been removed, return to “Initial Tasks”

on page 149. If it has not, replace the LCD as follows.

LCD Faulty If the elastomeric strips are not the cause of the fault, replace the LCD:

1. Disconnect the control-head loom. Remove the control-head board

and disassemble the control head.

2. Remove the LCD.

3. Use isopropyl alcohol and a soft lens-cleaning cloth to clean the

electrical contact points on the spare LCD. Carefully remove the

protective plastic film from the LCD. Take care not to scratch the soft

polariser material on both sides of the LCD.

4. Re-assemble the control head.

5. Reconnect the control-head loom and test the user interface. If the

fault has been removed, return to “Initial Tasks” on page 149. If it has

not, go to Step 6.

6. The control-head board is suspect. Level-1 service centres should

replace the board. Level-2 service centres should attempt to repair the

board as follows.

Tait TM8110 Service Manual

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