434
Fault Finding of Control Head with 1- 2- or 3-Digit Display
TM8100/TM8200 Service Manual
© Tait Electronics Limited
June 2006
15.3
All LEDs Faulty
If the display functions correctly but all the LEDs are faulty:
1.
Disconnect the control-head loom.
2.
Replace IC3 which drives the switching transistors for the LEDs.
See
.
3.
Reconnect the loom and test the user interface. If the fault has been
removed, return to
. If it has not, replace
the control-head board and return to
15.4
Display and All LEDs Faulty
If the display and all LEDs are faulty:
1.
Use a multimeter to measure the 3.3 V DC supply voltage across C1
(see
). If it is correct, go to
. If it is not, go to
2.
Check for shorts to ground of the 3.3 V supply. Repair any fault and
go to
3.
Use the multimeter to check that the
RST
line at pin 6 of IC7 is high.
The level should be 3.3 V. If it is, go to
. If it is not, go to
4.
Check for continuity in the LCD driver circuitry D22 (not fitted for
3-digit control head), C12 and R27 (see
). Repair any
fault and go to
. If there is no continuity fault, replace IC7 and
5.
Use the multimeter to check that the
OE
line at pin 8 of IC5 is low.
The level should be less than 0.6 V. If it is, replace IC7 and go to
. If it is not, go to
.
6.
Check that the voltage at pins 4, 10 and 14 of IC5 is 3.3 V DC.
Also check that pin 7 of IC5 is at ground. If the voltages are correct,
replace IC7 and go to
. If they are not, go to
.
7.
Check for continuity between IC5 and the control-head connector
SK1. Also check for shorts to ground between IC5 and SK1. Repair
any fault and go to
.
8.
Confirm the removal of the fault. If the fault has been removed,
return to
. If it has not, replace the
Summary of Contents for TM8235
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 04 Issue 4 June 2006...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 62: ...62 Description TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 148: ...148 Disassembly and Reassembly TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 162: ...162 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 178: ...178 Interface Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 258: ...258 Receiver Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 446: ...446 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
