Farfisa Soundmaker

The Soundmaker

i got my Soundmaker at a flea-market for a shockingly low price.
It had several problems when i got it, some of the hex inverters in the switch latching circuits were broken, a few LEDs were dead, The keyboard contacts needed a good clean and there was a missing note in the poly section.
The sliders were all scratchy, but they cleaned themselves up with a bit of exercise.
The missing note in the poly section was a dead Tantalum capacitor which had gone open circuit.

Now my Soundmaker is in perfect working condition, but for how long is it going to stay that wayt?

Tantalum Time Bombs

The soundmaker consists of three distinct synths, a monophonic synth, a polyphonic Divider synth and a string synth.

The monophonic synth is based on an m110 keyboard scanner/oscillator and a ca3080 based lowpass filter.

The polyphonic synth and the string synth are based on a top octave divider, and a series of trigger circuits, one for each note. these are made with 62 small pcb modules ,the PA902, the PA-902/1 and the PA-794 they each contain 4 tantalum capacitors, for a total of 244 capacitors. Tantalum capacitors don't age well, and one of their common failure modes is explosion. for this reason it's best to replace *all* of them. that's a lot of soldering and a lot of time.
There are still a dozen or so other tantalum capacitors to change on the other pcbs.

Heretic!

A sloppy back of the envelope calculation showed that it would probably take less time and cost less for me to design replacement PCBs with modern surface mount Tantalum capacitors, and have them manufactured in china than it would to simply replace the THT tantalum capacitors.
after counting the capacitors (244) i decided that this would be worth doing, and it turns out that not only are they cheaper than replacing the THT Tantalum capacitors by hand, but it's also a lot less work. the design part took ages though,it was my first time designing something to be assembled by a robot.

The golden ears