Tait TP9100 Service Manual

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272 CODEC and Audio Fault Finding TP9100 Service Manual© Tait Electronics Limited May 2005Task 3 ó2.5V Power SupplyIf the 7.5V (7 V 5 LINK) and 3V supplies are correct, the remaining powersupply to check is the 2.5V DC supply (+2V 5 CDC).1. Measure the voltage +2 V 5 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 theregulator as described in Task 4 of “Power Supply Fault Finding” onpage 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” (modulationat accessory connector only)Further details are given in the introduction to the section.12.2 Faulty Speaker AudioIntroduction This section covers the case where the green status LED is operatingcorrectly and all unmute criteria are satisfied, but there is either no speakeraudio 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 signalpin 5 of IC605: 2.5 ± 0.3V DC