TM8100/TM8200 Service Manual Frequency Synthesizer Fault Finding 195
© Tait Electronics Limited June 2006
Task 9 —
DIG SYN EN Line
If the supply for the charge pump and the reference frequency are correct,
check the
DIG SYN EN line input.
1. Check the
DIG SYN EN line at pin 10 of IC503 (see Figure 9.2).
Enter the CCTM command 334 0 to switch off the synthesizer, and
measure the voltage at pin 10.
2. Enter the command 334 1 to switch on the synthesizer, and measure
the voltage again.
3. If the voltages measured in Step 1 and Step 2 are correct, go to
Tas k 10
. If they are not, go to Step 4.
4. Remove R104 (see Figure 9.7) and repeat the above measurements
as follows:
5. Enter the CCTM command 334 0 to switch off the synthesizer, and
measure the voltage at the via between R104 (see Figure 9.7) and
the digital board.
6. Enter the CCTM command 334 1 to switch on the synthesizer, and
measure the voltage at the via between R104 (see Figure 9.7) and
the digital board.
7. If the voltages measured in Step 5 and Step 6 are still not correct, the
digital board is faulty; replace the board and go to “Final Tasks” on
page 157. If the voltages are correct, go to Step 8.
8. There is a fault between the digital board and IC503. Locate the fault.
Check and resolder R104 in position (see Figure 9.7), and check for
continuity between pin 10 of IC503 (see Figure 9.2) and the digital
board via R104.
9. If there is a fault, 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.
pin 10 of IC503: 0 V DC (after entry of CCTM 334 0)
pin 10 of IC503: 2.5 ± 0.3 V DC (after entry of CCTM 334 1)
via at R104: 0 V DC (after entry of CCTM 334 0)
via at R104: 3.3 ± 0.3 V DC (after entry of CCTM 334 1)
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