Pro 106 with no audio - bad DAC?

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johnmbb

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Nov 27, 2012
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I got a Pro 106 that had a bad DSP chip and wouldn't startup past the "DSP Loader" message. After replacing the DSP it seems to be working except that there is no audio. There is a good audio signal at the demodulator IC and all the signal strength bars show on the display when I tune to a local radio station and the squelch is open with the squelch indicator on the display. The audio amplifier is good too. Could there be a problem with the TLV320aic13c ADC/DAC IC? I don't have a service manual, and I can't find any traces coming out of the digital-to-analog pins, so I am not sure where the audio is supposed to come back from the logic board. Does anyone have a service manual for this who could help me out?
 

johnmbb

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Joined
Nov 27, 2012
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8
Update: I started to receive audio after finding that my pll or vco chip was not giving a frequency lock detect pulse to the cpu and the squelch was not opening until I manually gave the cpu the squelch open voltage. It is strange that it needs both of those things to happen before any audio is heard. It looks like I will need a new squelch potentiometer and 1.5 volt regulator for the dsp core. Those parts may not be available, but I will see if there are any alternatives.
 
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