Tait TM8100 mobiles, Service Manual

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418 CODEC and Audio Fault Finding TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 13 —
Check 2.3V Supply
If the
CH MIC AUD
signal is not as expected, the 2.3V supply needs to be
checked.
1. If not already done, remove the
CDC BOT
can.
2. Check the voltage across C202 (see Figure 13.9 ):
3. If the above voltage is correct, go to Task 14 . If it is not, go to Step 4 .
4. Check the soldering of R209 , and check for shorts to ground at C202
(see Figure 13.9 ). Repair any fault.
5. Confirm the removal of the fault and go to “Final Tasks” on
page 163 . If the repair failed or the fault could not be found, replace
the board and go to “Final Tasks” on page 163 .
Task 14 —
Check Bias Network
If the signal at the
TP
503
test point is incorrect, but the other checks in the
above tasks reveal no fault, check the bias network.
1. Remove the
CDC TOP
can.
2. Check the voltage at the junction of R229 and R232
(see Figure 13.10 ):
3. If the voltage is correct, go to Step 4 . If it is not, go to Step 5 .
4. CODEC 1 ( IC204 ) is faulty; replace the board and go to “Final
Tasks” on page 163 .
5. Check the soldering of R229 and R232 , and check for shorts across
R232 (see Figure 13.10 ). Repair any fault.
6. Confirm the removal of the fault and go to “Final Tasks” on
page 163 . If the repair failed or the fault could not be found, replace
the board and go to “Final Tasks” on page 163 .
voltage across C202: 3V
junction of R229 and R232: 1.5V DC