Looks like the TC9152P has gone leaky. Between 6 and 14V with high source impedance present at the two output pins. As it's a bilateral switch, this also backfeeds into the sources and phono stage. The 'tuner' input does not couple signal through at all. I've got audio from the tuner board when signal tracing.
This DC leakage gets thru the coupling caps for opamps IC452/453, since they are the 'wrong' way around. With DC offset and their bias upset, the audio is rather distorted. Feeding a source into the tape inputs bypasses the TC9152 and the output signal is fine.
But wait, there's more! One or more of the opamps in the big bank for the 'Sonic Holography' may also be leaky. When engaging into the signal path, there is a pop in both channels. Immediately, right goes dead and left still has signal, but no effects can be heard whatsoever. This backs up my guess of bad opamps...
PDFs too big, so links are here:
-Paul
This DC leakage gets thru the coupling caps for opamps IC452/453, since they are the 'wrong' way around. With DC offset and their bias upset, the audio is rather distorted. Feeding a source into the tape inputs bypasses the TC9152 and the output signal is fine.
But wait, there's more! One or more of the opamps in the big bank for the 'Sonic Holography' may also be leaky. When engaging into the signal path, there is a pop in both channels. Immediately, right goes dead and left still has signal, but no effects can be heard whatsoever. This backs up my guess of bad opamps...
PDFs too big, so links are here:
-Paul
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