Tait TB7100 - Page 347

TB7100 Service Manual CODEC and Audio Fault Finding 349
© Tait Electronics Limited October 2005
Task 5 —
Check Speaker
Outputs
If the inputs to the audio PA are not faulty, check the speaker outputs from
the PA.
1. Check the positive and negative speaker outputs
AUD ITF SPK+ and AUD
ITF SPK– at pins 3 and 8 respectively of IC202 (see Figure 15.2):
2. If the speaker outputs are correct, go to Step 5. If they are not, go to
Step 3.
3. Check for and repair any soldering faults around IC202
(see Figure 15.2), or else replace IC202.
4. Confirm the removal of the fault and go to “Final Tasks” on
page 123. If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123.
5. With the volume at maximum, check each speaker output at pins 3
and 8 of IC202 (see Figure 15.2):
6. If the speaker outputs are correct, the fault is unknown (it could be
intermittent); replace the main-board assembly and go to “Final
Tasks” on page 123. If there is no AC, go to Step 7.
7. Check that C204 and R214 (see Figure 15.2) are not faulty and are
correctly soldered. Repair any fault.
8. Confirm the removal of the fault and go to “Final Tasks” on
page 123. If the repair failed or the fault could not be found, replace
the main-board assembly and go to “Final Tasks” on page 123.
pin 3 of IC202 (AUD ITF SPK+): approximately half-rail bias
pin 8 of IC202 (AUD ITF SPK–): approximately half-rail bias
pin 3 of IC202 (AUD ITF SPK+): approximately 9.5V
pp
AC
pin 8 of IC202 (AUD ITF SPK–): approximately 9.5V
pp
AC