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
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