PCB Corrosion Clean Up

Question

Any advice on cleaning up this PCB corrosion or fixing this board?

This is on a CR-814 stereo form a 1994 Volvo 940.

Audio is fine when the stereo is powered on. After a few seconds the front right speaker clicks at ~ 1 Hz. The frequency of the click occurrence increases slowly till it becomes a high pitched whine. The whine increases in frequency, then after maybe 20 minutes it becomes inaudible all of a sudden and audio is fine.

Perhaps some flux didn't get cleaned up. Maybe a component leaked? I don't know what the 3 legged "50" component is. The rest of the boards look fine, and the enclosure is well built and intact. The problem area is in the center of a protective bit.

The black corrosion has a liquid component. A gentle touch with a screwdriver pulls the sludge off. I find the white corrosion on the solder very interesting.

My best guess would be to dam the area to prevent collateral damage, and scrub with isopropyl alcohol 90%. I'd hope this removes any shorts that are occurring between components through the liquid. Maybe I'd find a fully corroded solder joint.

Answer 1

Try IPA if that doesn't work get some tech-spray flux remover which is a good solvent for cleaning PCBs.

A little acetone could also get it but also damage parts on the PCB so be careful.

Answer 2

That looks more like the circuit is overheating. I see what looks like tiny droplets of solder. Try cleaning it with the alcohol and a stiff brush so you can get a better look at the circuit traces, but I suspect you'll find a component has gone bad. As @RussellH said, you may have a defective electrolytic capacitor.