Repair Sequential Circuits Six-Trak Vintage Analog Synthesizer Reparatur
This Sequencial Circuits Six-Trak had a few issues. Main Issue was, the Six-Trak wasn't booting. One voice was missing and some of the input buttons weren't working. One voice was missing because of a faulty 4051 cmos ic. That these type of integrated circuits go bad happens quite often. Replacing that one little component brought the voice back to life. Much harder to solve could be the next issue. Usually I can refurbish such rubber contact buttons very well. I can tell, it worked this time as well, but initially I thought this time I would have no success. I show you why.
This little 1N4002 diode was responsible for the boot problems. It sits in the +5V rail of the RAM chips. If the RAM chips are not working the synth cannot start.
This picture shows an old, but healthy button of a Sequencial Circuits Six-Trak. That's how the usually should look like when you inspect them.
But most of the contacts were hardly scratched and so far somewhat damaged by some previous person, not me! This picture shows one of the worst damage. Lucky me, there is enough existing material for the buttons to make contect when pressed down to these fingers. Please, never ever scratch those contacts or use sand paper or any kind of rough material.
The correct way is to refurbish these contacts on the rubber side of the contacts. These contacts have an electrical resistance and if it goes to high, because they were worn out, the circuit doesn't recognize the pushed button, so there is no function any more. So if you experience some of your synthesizer buttons are no longer in good shape, don't hesitate to contact me about yout synth situation.
Other than that I just spotted some weak looking solder joints which I just re-flowed. Service!
There are 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 computer and other vintage gear, based in Düsseldorf, GER. Get in touch about your synth situation!