Restortion of an 80’s ultrarare Solton Disco 64.
The cosmectic condition the the Solton was not really like mint. There was corrosion and substances from moisture like everywhere. On the electrical side there were also some issused and also some “custom wishes”.
After some testings I decided to clean the keyboard first. I took it apart and cleaned everything. The buswires, the springs, connectors, keys, housing. So condition is nearly like new now and the keybord is fully working. I have several methods for this but usually a rubber pencil and IPA works great.
Next I addressed the buttons. 2 of them weren´t working and while desoldering them they fell into pieces because of heavy corrosion. Usually I had to replace them all, but since they are not available anymore and the other were still working, I constructed 2 replacements by using micro tactiles. Works great, nice “push” feeling.
I also replaced all corroded wires on these pcbs and reflowed all solder joints.
But since still not all buttons were working I figured out that the key assigner IC Siemens SM 304 A were faulty. I replaced that with NOS. Now all push buttons were fully working.
Next I addressed the missing voices. A mix of faulty logic ICs and OpAms and some weak solder joints on the voicing board were the reason for this issue.
Ok, while I was in here I found some leaky caps and decided to do a whole re-cap on this Solton.
All potentiometer were crusty so I decided to replace them too.
I replaced the big 10W resistor in the psu. I replaced the 5V rail with a modern step down module which got barely warm. The old resistor also destroyed the 2 ceramtic fuse holders and the fuses. While checking them they fell into pieces like glass. This restistor was hot like hell. I measured 100°C after a few minutes. It was there to drop down the voltage for the old 5V regulator. Now it`s no longer needed.
My customer also wanted to have individual audio outs and digital trigger outs. I added a small board with transistor pre-amps.
I replaced the line filter cap with a modern safety filter cap.
Disclaimer: There could be lethal voltage exposed in electronic devices. Unless you know what you are doing, don’t try this. If you following along, you doing so at your own risk.
I’m documenting repairs for my reference and yours.
I do synth restorations and repair with a specialty in vintage synthesizers, drum machines and other vintage gear, based in Düsseldorf, GER.
Get in touch about your synth situation!