Tait TB7100, Service Manual

Page: 155 / 370

TB7100 Service Manual Frequency Synthesizer Fault Finding 157
© Tait Electronics Limited October 2005
Task 8 —
Reference
Frequency
If the supply for the charge pump is correct, check the reference frequency
input from the FCL to the PLL.
1. Measure the reference frequency at pin 8 of IC503
(see
Figure 11.2 ).
2. If the signal is correct, go to Task 9 . If it is not, go to Step 3 .
3. Check IC503 (see Figure 11.2 ). Replace IC503 if it is suspect.
4. Determine if the fault has been removed. If it has, go to “Final Tasks”
on page 123 . If it has not, the FCL is suspect; go to “Power Supply
for FCL” on page 189 .
Figure 11.6 Components between the digital board and the frequency synthesizer
VIAS FOR
MEASUREMENTS
FCL TOP CAN
pin 8 of IC503: 13.012
±
0.002 MHz and 1.1
±
0.2 V
pp