Tait TP9100 - Page 286

286 CODEC and Audio Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 14 —
Check External
(Accessory)
Microphone DC Bias
To check the DC bias on the external microphone:
1. Check the DC level on the +3
V0 FIL signal at the junction of R209
and C202 (see Figure 12.5):
2. If the DC level is not present, check the components and soldering
of R209 and C202 (see Figure 12.5). If the signal is present, go to
Step 4.
3. Confirm the removal of the fault and go to “Final Tasks” on
page 134. If the repair failed or the fault could not be found, replace
the main board and go to “Final Tasks” on page 134.
4. Check the DC levels at the junction of R226 and C213, also the
junction of R229 and C213 (see Figure 12.3):
5. If either DC level is not present, check and repair the components and
soldering around R226, R229, R232, and C213 (see Figure 12.3).
If both DC levels are correct then the fault is between E901
(see Figure 12.1) and R226/C213. Replace the main board and go
to “Final Tasks” on page 134.
6. Confirm the removal of the fault and go to “Final Tasks” on
page 134. If the repair failed or the fault could not be found, replace
the main board and go to “Final Tasks” on page 134.
junction of R209 and C202: 3.0V ±0.2V (typical)
junction of R226 and C213: 3.0V ±0.2V
junction of R229 and C213: 1.5V ±0.2V