TB7100 Service Manual CODEC and Audio Fault Finding 361
© Tait Electronics Limited October 2005
Task 11 —
Check
QN Test Point
If the level shifter is not faulty, check the signal at the QN test point. This will
ascertain whether the digital board, 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 at the
QN test point (there is access
through a hole in the
IF TOP can — see Figure 15.8).
4. If there is a sine wave present, go to Step 5. If there is not, go to
“Receiver Fault Finding” on page 201.
5. Either the digital board or CODEC 1 (IC204) is faulty; replace the
main-board assembly and go to “Final Tasks” on page 123.
QN test point: sine wave
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