I've been trying to revive an Aiwa HS-J9 main board. It and the adjacent motor board were badly corroded by leaking batteries. The motor board was a complete write-off with half the traces gone. With a replacement motor board (and a lot of other work), the tape drive seems to work as it should. So the logic section of the main board must be ok. The power led lights up but I can't get any sound from either the radio or the tape drive. The equalizer is bad. I know from the circuit diagrams and testing on another unit, that bypassing the equalizer works and does no harm. But bypassing the equalizeer on the corroded unit does not fix it. Next I'm going to try bypassing the Dolby circuitry. So far I've found and repaired one corroded trace on the main board. There is corrosion inside the tuner, and adjacent adjustment pots, so it's not surprising the radio doesn't work. I put the ruined motor board in undiluted white vinegar. The corrosion bubbled and dissolved in a couple of hours. I brushed off the loose stuff and put it back in the vinegar. I didn't know if that completed the treatment, because continuing discharge of whiteish residue indicated there was still matter being dissolved. After a while I suspected the vinegar might be eating things that should not be, so I rinsed and dried the board. All exposed solder points looked dark dull grey. I'm looking for advice on whether to dilute the vinegar, and at what point the treatment changes from completing its work and starts doing damage. Most depictions of this work show people brushing with something like a toothbrush. I don't see how that can clean under IC's unless they are removed.
