CD63KI problems - please help

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If you don't see anything on the RF (not that you should) when it does drop out then the problem is looking a bit deep seated and obscure.

I guess the next step is to use the scope to monitor the audio as early in the process as possible, which will be the output of the DAC's.
 
Thanks for the suggestion to work back from outputs.
I have resoldered the TCA driver chips - as well as all caps and resistors on laser board, around the outputs and before and after the DAC chip. Removed opamps and tried with each channel disabled to eliminate the possibility of opamp failure.
I detected a 2.5v presence at the DAC pin 26 where 5v should be present....??
 
Is this 2.5 volts at some different value when the fault occurs ? In other words does it alter according to the fault.

Sorry for the long delay in replying to your response.
I have since found that a resistor of incorrect value was used - and this reduced the voltage from 5v to 2.5v. The correct resistor has been intalled. The voltage is now corrected to 5v as per service manual. The voltage does not alter according to the fault.
 
Problem persists!
Had some time to look a CD63KI again - have noticed that at audio drop out voltage(s) at pin1 or both opamps changes from 0v to 0.5v (Left channel ) and 1.6v (right channel). Depending on cd being played. Voltages have fluctuated on pin1 of both opamps from 0.5v up to 2.6V!!????
 
Hi again Mooly, I have been fortunate to receive a 50mhz scope from a friend! Still learning how to use all the controls and can now look at cd63ki with a little more confidence.
I also noted at audio drop out pin1 (both opamps) has a voltage change from 0v to 0.5v and 1.6v even as high as 2.6v!! depending on what cd is being played.
 
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I really don't know what to suggest to you with this problem, its obscure and deep seated.

Its always worth checking supplies when anything odd happens. Check the rails to the opamps with the scope and see if anything shows on either rail when the drop out occurs. Do the same for any supplies to the DAC. It probably has more than one supply.

If that gets nowhere then you have to use the same technique and go around all the pins on the DAC with the scope and see if anything shows when the drop outs occur. Its then a matter of interpretation as to whether anything observed is a fault or whether its the DAC responding to a problem elsewhere. It could be anything I'm afraid.
 
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