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Old Crow's Synth Shop: Polysix KLM-367 Board Repair

WARNING: I can't stress this enough. The procedure now involves cutting away damaged circuit traces with a sharp X-acto knife. This is tricky, sometimes hazardous (I've gotten cut more than once over the years) and time-consuming. If you are not up to it, get a friend who is.

Step 4: Cutting Away the Damaged Traces

NOTES: before excising a trace, first take the knife and 'nick' the trace at one end. This is so that when the trace is peeled up, it will stop peeling at the right place. Once this is done, take the knife and make a sharp cut across the trace at the point you wish to start removal. Once this is done, use the tip of the knife while keeping the blade level with respect to the board to 'dig' under the sharp cut. After a few tries, the trace with 'catch' on the blade and start to roll up into a tight spiral. If you can get enough of the trace started coming up, use your fingers and try to gently pull on the 'tail' of the trace and it will peel right off the board, breaking off where the 'nick' was made.

Some traces are not so cooperative. The blackened ones often have most of the copper weakened to the point that they do not peel up, they crumble from board. In this case, you have to carefully excavate the trace using the knife and a lot of patience. Do not dig deep into the glass-epoxy board material; the traces are all on the surface under the soldermask. Also, some traces tend to come up in short segments. Use a combination of digging and peeling to get these off the board.

If you can get ahold of a 'junk' circuit board, practice on it!

4-1: Start by cutting the short, thin traces near IC31. Do not worry if you pull up the top-layer solder pads; they are not going to be used anymore.

4-2: Next, proceed to the longer traces. If there is a via (pad hole) along the trace, you can either stop there or, if the pad is in the middle of a bad section, stop there and start again on the other side of it.

4-3: Finally, remove the thick traces. These are the toughest to cut, but tend to be the easiest to remove once started.

Here is a closeup of the board after removing most of the traces marked on the tracemap.

4-4: Once again, clean the area with a brush and alcohol.

Step 5: Preparing the Mounting Holes

Scott Rider --