TM8100/TM8200 Service Manual CODEC and Audio Fault Finding 397
© Tait Electronics Limited June 2006
Task 11 —
Check QN Tes t P o in t
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 13.8).
4. If there is a sine wave present, go to Step 5. If there is not, go to
“Receiver Fault Finding” on page 239.
5. Either the digital board or CODEC 1 (IC204) is faulty; replace the
board and go to “Final Tasks” on page 157.
Figure 13.8 Circuitry in the vicinity of the CDC TOP can (UHF shown)
Junction of
C708 and C732
QN test point: sine wave
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