Discussion about the Korg PolySix synthesizer

There is some obvious corrosion on the data line traces by the 74LS08 chip next to the battery. This battery wasn’t replaced until after the old one started leaking, and it doesn’t look like anything was done to neutralize the alkaline liquid from the battery. The corrosion is probably still spreading.

Don B.

 

What I would suggest is to get the board out of there and put some vinegar (a weak acid) on the area around the battery to neutralize it, then rinse it off with a zero-residue contact cleaner (not the kind with added lubricants in it). Then you will need an ohm-meter to check all of those blackened traces under the 74LS08 chip. The chip is probably toast and will need to be removed. It would be best to put the replacement chip in a socket, so you solder the socket to the board and just pop the chip in without any unnecessary heat applied to the chip. Any traces on the board that measure more than a fraction of an ohm will need a jumper wire soldered in to replace them. Sorry if this sounds complicated, but if you know what to look for, there is quite a bit of damage. Solder points should be shiny silver, not powdery gray. Copper traces on the board should be copper colored (although a bit greenish since they are under that green coating that covers the board), not blackened. The stuff that comes out of a leaked battery is just a couple of drops and spreads like penetrating oil. It might not look wet at all. It sounds like the battery was replaced before it caused any obvious damage, but not before it leaked. Now it has had 10-15 more years to wreak havoc. There are two of those 74LS08 chips in there, but I couldn’t tell from the video if the other one also has damage around it.

Don B.