Repair EKO EKOsynth P15 Vintage Analog Synthesizer Reparatur Service25. Juli 2020
Repair ROLAND Promars Compuphonic MRS-2 Reparatur Service30. Juli 2020
EMU Emulator Vintage Sampler from the 1980's. This one is very big and heavy. Very solid build. Lots of digital stuff inside. It looks more complicated than a modern laptop. But only has 128kB (yes, kilobyte!) of sampling RAM, which is aprx. 2s (yes, seconds!) of sampling time, at 8 bit resolution. Condition: no audio output except 50Hz hum.
It turned on and it sounds (and looked) like the system booted from 5" floppy diskettes (!) and the sounds could be loaded. The "get upper" and "get lower" leds were lighting up. That usually means sounds were loaded.But playing the keybord had still no sound on the output except 50Hz hum.
The first thing I suspected was the power supply. And yes, the +15V rail was shorted. But this also meant to check, if it was the psu itself or any of the connected boards. And, yep, it was not the psu but one of the boards. The psu looked recapped to me, so I left the capacitors in but it looked to me the thermal paste wasn't renewed at theat time. So I did this.
I could narrow down the short to the audio sample input board. One capacitor was bad but this was not the culprit. The faulty compoment was a healthy looking tantalum capacitor. These typically short when they go bad. While I was in here I checked all components and also found a dead LM311 which is part of the sampling process. I also found some weak solder joints on the switch board. Loading the lower sounds wasn't working. But now everything works fine again..
The keyboard wans't in great shape. Some keys didn't make good contact. The key bushings were worn out. I replaced all the key bushings and gave it a good cleaning.
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!