Tait TP9100 - Page 169

TP9100 Service Manual Frequency Synthesizer Fault Finding 169
© Tait Electronics Limited May 2005
Tas k 6 —
3V Power Supply
If the SMPS output and the 5V and 4.3V supplies are correct, the remaining
power supply to check is the 3V DC supply.
1. Measure the supply +3
V0 AN at pins 7 and 15 of IC503
(see Figure 9.3).
2. If the voltage is correct, go to “Phase-Locked Loop” on page 170.
If it is not, go to Step 3.
3. Check the supply at L506 (see Figure 9.3). The measurement point
is the via shown in the figure.
4. If the voltage is correct, go to Step 7. If it is not, the 3V regulator
IC604 is suspect (see Figure 9.4).
5. Measure the voltage
DIG 3VANEN at pin 3 of IC604 (see Figure 9.4).
6. If it is correct, go to Step 7. If it is not correct, go to “Power Supply
Fault Finding” on page 149.
7. Check the components in the path from L506 to IC503. Also check
IC503; if necessary, replace IC503 (see Figure 9.3).
8. If a fault is found, 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.
pins 7 and 15 of IC503: 2.9 ± 0.3V DC
L506: 2.9 ± 0.3V DC
L506: 2.9 ± 0.3V DC
Figure 9.4 Location of the 3V regulator IC604 (bottom side)