TP9100 Service Manual CODEC and Audio Fault Finding 287
© Tait Electronics Limited May 2005
12.6 Faulty Modulation Using Accessory Audio Tap In
Introduction This section covers the case where the transmitter operates normally but
there is no modulation from
AUD TAP IN (although there is modulation at the
accessory connector). There are two tasks:
■ Task 15: check AUD TAP IN path
■ Task 16: check audio and modulation
If there was also a fault with the speaker audio at the accessory connector, it
is assumed that this has now been rectified.
Task 15 —
Check
AUD_TAP_IN
Path
To check the AUD TAP IN path:
1. Check the connector PL1 (see Figure 12.1) and the flexible acces-
sory board connection to the main board as defined in “Accessories
Interface Faulty” on page 147. Assuming this is correct, proceed to
Step 2.
2. Check the DC offset voltage at pin 8:
3. If the offset is correct, go to Task 16
. If the offset is not correct go to
Step 4
4. Check and repair the components and soldering around PL1, E902,
and C911 (see Figure 12.1).
5. Confirm the removal of the fault and go to “Final Tasks” on
page 134. If the repair failed, go to Step 6.
6. Check for and repair any soldering faults around IC205 and R241
(see Figure 12.3).
7. Confirm the removal of the fault and go to “Final Tasks” on
page 134. If the repair failed, go to Step 8.
8. Check the DC offset voltage at pin 3 of IC205:
9. If the offset is correct, IC205 is okay but there is a fault between
IC205 and PL1. Recheck soldering and components R241
(see Figure 12.3), E902, C911 (see Figure 12.1). If the offset is not
correct, replace IC205.
10. 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.
pin 8 of PL1: approximately 1.5V DC offset
pin 3 of IC205: approximately 1.5V DC offset
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