Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual CODEC and Audio Fault Finding 415
© Tait Electronics Limited November 2007
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 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 247 .
5. Either the digital board or CODEC 1 ( IC204 ) is faulty; replace the
board and go to “Final Tasks” on page 163 .
Figure 13.8 Circuitry in the vicinity of the
CDC TOP
can (UHF shown)
Junction of
C708 and C732
QN test point: sine wave