This Arp Pro-DGX Monophonic Analog Synthesizer came in for repair as “non working”. PSU was already re-caped. Synth turned on but no other signs of life.
For better trouble shooting I layed all the pcbs across my bench.
I then found out that the keyboard electronic wasn´t working. It took me a while to dignost, which logic ICs weren’t working. Let’s say, I had to replace at least 50%. At one time the synth came back to life, but only for “auto trigger”. So I had to replace two more logic ICs, and I also had to clean the keyboard contacts and I also had to adjust these.
I decided to replace the tantalum caps with electrolytic in some places. One transistor looked damage, but wasn´t. Cleaned and lubricated the sliders, pots and switches. Made sure the modulation strip was also working well.
I made some minor calibration/adjustments. Synth is fully working and customer is very happy.
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. Bring it to a qualified tech. Bring it to me.
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!