I picked up a 1965 Farfisa Combo Compact organ from Craigslist a few weeks ago for $100.  This weekend, I decided to replace all the original electrolytic capacitors with new ones, as there were visible signs of leakage on some of them.  There was also some strange behavior from the keyboard that I hoped to fix, including a weak vibrato and some voices not working on certain notes.

I opened it up and found that somebody had gutted the power supply / preamp and rigged up a 9V regulator.  It works, but there’s no tube reverb driver circuit anymore.  Not a huge deal, as this Compact is missing the spring reverb tank anyway.  They may have tried to run this thing on a 9V battery, as evidenced by the 9V battery harnesses.  I haven’t tried it, but I assume it would work for a few minutes until the battery died.

The guts of the Farfisa lift out after unscrewing three wing-nuts underneath.  This allows access to the PCB cards from the back.

Here’s the vibrato / pedal amplifier card pulled out.  It’s not a very elegant design, as everything is connected through about a mile of wiring internally, but it does make it relatively easy to service.

I also decided to recap all twelve oscillator cards.  These cards produce each of the twelve notes, and are labeled accordingly.  Tuning is adjusted by turning a threaded inductor core.  This is the “F” card.  There are six 1uF capacitors, a single 25uF, and a 50uF on most cards.  Some cards didn’t have the 50uF cap, and the “C” card has an extra 1uF capacitor, mounted axially.

There are twelve Germanium transistors on each card as well.  I see why people part these things out now, as you could probably sell each transistor for a couple bucks to people who build vintage-style guitar pedals.  That’s what gives these 60′s combo organs their unique sound.

Here’s the pile of caps I had removed after I was finished.

While I was in there, I also cleaned the key contacts with some spray contact cleaner.  I fired it up and it solved all the issues I was having.  It has a much better frequency response overall, especially in the bass notes, and it has a much more “cutting” tone when at maximum boost.  I tweaked the vibrato speed to have a greater difference between “slow” and “fast.”  It also needed to be tuned again, as almost every note was about a half-step flatter than before the recap job.  It was well-worth the effort, and really only took a few hours to do with the help of my trusty Hakko 808 desoldering gun.