Tait TP9100 - Page 172

172 Frequency Synthesizer Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
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
Ta sk 1 0
. If they are not, go to Step 4.
4. Remove
DIG BOT can.
5. Enter the CCTM command 334 0 to switch off the synthesizer, and
measure the voltage on both sides of R716 (see Figure 9.6).
6. Enter the CCTM command 334 1 to switch on the synthesizer, and
measure the voltage on both sides of R716 (see Figure 9.6).
7. If the voltages measured in Step 5 and Step 6 are still not correct,
check whether the IO port (D2) of IC701 is faulty or shorted by
solder. If the voltages are correct, go to Step 8.
8. If there is a fault, repair the circuit, confirm the removal of the fault,
and go to “Final Tasks” on page 134. If the repair failed or no fault
could be found, replace the main board, and go to “Final Tasks” on
page 134.
pin 10 of IC503: 0V DC (after entry of CCTM 334 0)
pin 10 of IC503: 2.5 ± 0.3V DC (after entry of CCTM 334 1)
R716: 0V DC (after entry of CCTM 334 0)
R716: 3.3 ± 0.3V DC (after entry of CCTM 334 1)