272 CODEC and Audio Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 3 —
2.5V Power Supply
If the 7.5V (7V5 LINK) and 3V supplies are correct, the remaining power
supply to check is the 2.5V DC supply (+2
V5 CDC).
1. Measure the voltage +2
V5 CDC at pin 5 of IC605 (see Figure 12.3).
2. If the voltage is correct, go to Step 4. If it is not, go to Step 3.
3. The 2.5V regulator IC605 is suspect (see Figure 12.3). Check the
regulator as described in Task 4
of “Power Supply Fault Finding” on
page 156.
4. Proceed to the section relevant to the fault exhibited:
■ “Faulty Speaker Audio” (distorted or no speaker audio)
■ “No Audio Tap Out at Accessory Connector”
■ “Faulty Receiver” (receiver does not operate)
■ “Faulty Modulation” (distorted or no transmit modulation)
■ “Faulty Modulation Using Accessory Audio Tap In” (modulation
at accessory connector only)
Further details are given in the introduction to the section.
12.2 Faulty Speaker Audio
Introduction This section covers the case where the green status LED is operating
correctly and all unmute criteria are satisfied, but there is either no speaker
audio or the speaker audio is distorted. There are three tasks:
■ Task 4: check audio power amplifier
■ Task 5: check speaker outputs
■ Task 6: check SUI VOL DC input signal
pin 5 of IC605: 2.5 ± 0.3V DC
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