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« Last post by downunder on November 28, 2022,01:59:34 »
IC3002 + IC3906: Input pin is 8 = 5.8V, Output pin is 1 = 5V, On/Off Switching pin is 5 = high . This is the same in all modes i.e Play, Stop, Rec.
IC3906: Input pin is 4 =5.8V, Output pin is 1 = 5V, On/Off is pin 3 = 4.6V in all modes.
QR4501 has 4.6V on the base only in all modes.
The service manual does have a voltage chart for all ICs .
I suspect it all comes back to Micro IC6001 not supplying switch-on volts from pin 75 to IC6302. I wouldn't attempt to remove the micro but with an injection of soldering flux under it and judicious application of a heat gun to the top of the IC you might get sufficient solder flow at the ball joints to remake any poor contact.