My Encore Frequency Shifter had been troublesome for years now. Sometimes it would come up with all lights bright and not working. It started doing this all the time, so I emailed Tony at Encore Electronics about it. Turned out this was a known problem as far back as 2011. There was a discussion about it on ModWiggler. The problem was with the -15V power distribution on the board, caused by a corroded via. Various approaches to fixing it were put forth. Once I took apart the modules, I came up with my own way.

The picture above shows the negative power inlet feeding to L1. On the other side you can see the trace has turned black as it goes by the 10uf bypass cap to the bad via.

I removed the bypass cap, C7. I suspect that C7 was leaking. There was some oil on the back side near the damaged via. It was clear what needed to be done.

I cleaned off the corrosion as best as I could, then set about replacing the capacitor and ensuring good conductivity for the negative rail.

I stuck the negative lead of a new 10uf 25V electrolytic cap through the bad via and soldered it to the circuit trace on the back side. Then I ran a jumper from that lead directly to L1, avoiding the messed up trace altogether. Finally, I soldered the positive lead onto the cleaned up ground pad.

Using the via just as a hole, not for conductivity, I soldered the cap lead onto a cleaned section of the trace. To the left in the photo is a second, possibly corroded via. I scraped that one top and bottom and used some solid bus wire to ensure that one would not cause trouble, either. All connections were tested for continuity before reassembly.