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TM8100/TM8200 Service Manual Frequency Synthesizer Fault Finding 185

Task 3 —

14V Power Supply

First check the output VCL SUPPLY from the SMPS, which is itself provided

with a 9V DC supply from a 9V regulator in the PSU module.

1. Remove the board from the chassis.

2. Place the radio in CCTM.

3. Measure the SMPS output

VCL SUPPLY at the via between C531 and

R530 (see Figure 9.2).

Note On A4 band radios, C531 and R530 are on the bottom side of the

PCB. Measure the

VCL SUPPLY voltage on the via beside C5050.

4. If the SMPS output is correct, go to Tas k 4

. If it is not, go to Step 5.

5. Check the 9 V supply at Q500 and R533 (see Figure 9.3).

6. If the voltage is correct, go to Step 7. If it is not, the 9V regulator

IC601 is suspect; go to Tas k 3

of “Power Supply Fault Finding” on

page 168.

7. Remove the

FCL TOP can and check the SMPS circuit based on Q500,

Q502 and L502 (see Figure 9.3).

Note On A4 band radios, these components are not located under the

FCL TOP can (see Figure 9.3).

Remove the

SYN BOT can and check IC504 and IC505 for shorts

(see Figure 9.4); replace any suspect IC.

8. If a fault is found, repair the circuit, confirm the removal of the fault,

and go to “Final Tasks” on page 157. If the repair failed or no fault

could be found, replace the board and go to “Final Tasks” on

page 157.

C531: 14.2 V ± 0.3 DC

Q500 and R533: 9.0 V ± 0.3 DC

Tait TM8115 Service Manual

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