Capacitor-leakage related repairs

[creatorlars]

I'm not sure where else to post this, I'm not aware of a "repair help/questions" forum, but please move my post if I've missed it for some reason.

I've had a disassembled Korg Micro-Preset on my shelf for over a year. I love how it sounds and want to get it back up to full speed. It works fine except for three of the preset patches (Synthe 1, Synthe 2, and String). My friend recently had one repaired for the same issue and said it was all due to capacitor leakage/broken traces. Reviewing the top-side of the PCB (parts and bare copper traces -- bottom has solder mask) I can definitely see some corrosion and discoloration on the traces around a few of the capacitors.

What is best practice for this kind of repair on a synth this old? (32 years) Should I replace all capacitors? Just electrolytics? Anything I should be especially careful about? Any tell-tale signs on the capacitors themselves (at first glance the caps themselves look fine.) I have schematics but they are a poor quality scan, but decent enough to squint and make a good enough guess on connections.

Thanks for any advice.

[Skrog Productions]

Hello Lars, the electrolytic liquid inside the cap canisters tends to dry up after a long time , try replacing those and cleaning the residue from them on the tracks and scrape a little extra of the mask away from the pads for a fresh contact for the new solder connections.

wash your hands after contact with electrolytic liquid, it's vile to your insides if ingested

[RF]

For a quick job, I'd probably just replace the larger electrolytics, all power supply caps, and any in the part of the circuitry that you know to be bad.

I don't often find bad small caps (ie. 10 uf or less) - and I do a good bit of troubleshooting of older equipment.

Besides the visible leaks - bad caps will often have bulging rubber on the bottom of the cap or a dome or split in the top metal.

good luck!

bruce

[creatorlars]

Great helpful advice from both of you, thanks so much! Time to bring out a notepad to start writing down cap values...