This Aiwa HS-J9 suffered corrosion damage near the battery compartment and into the tuner. I've gotten the tape drive to work, mainly by replacing the motor board. The power led lights up. There is no audio from the tape or radio sections. I'm trying to track down where the problem is. A) The equalizer is always suspect on these units. I have shorted Lin (2) to Lout (1),and Rin (3) to (4). This didn't fix the problem. If the EQ is faulty, should I be able to get audio this way? B) The Dolby circuitry may be faulty. Both the tape and radio circuitry go through the Dolby section. I don't know why the radio section goes through the Dolby circuitry. To check the radio against the Dolby I shorted Dolby IC5 pin 2 to EQ Lin (2), and Dolby IC5 pin 24 to EQ Rin (3). This didn't fix the problem. To check the tape against the Dolby I shorted Dolby IC5 pin 3 to EQ Lin (2), and Dolby IC5 pin 23 to EQ Rin (3). I also tried bypassing both the equalizer and Dolby at the same time by shorting EQ Lout and Rout to the Lin and Rin of the volume control. Usually I test just the left or right channels to make things simpler. Are these valid tests? Could I short the volume control's Lin and Lout, and Rin and Rout, to see if the volume control is faulty? I assume I would get maximum volume output if the volume control is ok. So I wouldn't use my best earphones. So far it looks like both the tape and radio sections are faulty, and/or the main amplifier is bad. (The earphone circuitry has been verified.) I have another known good HS-J9. With both powered on, could I feed its circuitry at various points into the same points on the faulty unit? Such as EQ Lout and Rout on the good unit, into EQ Lout and Rout on the faulty unit? Same with the tape, radio, Dolby, volume control and main amp circuitry? Could I also do this in reverse between the two units? Is there a risk of damage? If the signal source unit has no earphone plugged in, it shouldn't know the difference between output through its own circuitry and through the same circuitry of the target unit (also powered on)? The circuit diagram is for the J09. I know the circuits are a little different for the J9, but I'm hoping these major points are the same. I'm unable to find J9 diagrams.
