TP9100 Service Manual CODEC and Audio Fault Finding 283
© Tait Electronics Limited May 2005
Task 10 —
Check
QN Signal
If the level shifter is not faulty, check the QN signal. This will ascertain
whether the digital circuitry, CODEC 1, or the receiver is at fault.
1. Use the programming application to find the frequency selected for
channel 1.
2. Apply a strong on-channel signal.
3. Check that a sine wave is present using TP444 (see Figure 12.5).
4. If there is a sine wave present, go to Step 5. If there is not, go to
“Receiver Fault Finding” on page 251.
5. Either the digital circuitry or CODEC 1 (IC204) is faulty. Replace
the main board and go to “Final Tasks” on page 134.
TP444: sine wave
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