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Roland SRE-555 Chorus Echo Reverb restoration. Condition: No audio output. Well, it powered on and the tape was running. Thats always a good sign, means power suppy and motor were working. But there was no FX at all but a lot of hum.
Opening this thing up and I spotted these purple Matsushita caps again, which almost always leak. I replaced all. So one reason for the hum was eleminated.
Another problem causing hum is a bad connection to the reverb tank or, like here, broken wires in the tank. Which could easily be fixed.
The RCA jacks were also heavily corroded and cleaned. I found some bad Op-Amps, one 1/4 audio jack was broken and replaced. The pcb holding the 3 control leds was broken and fixed. New heatsink compound was applied.
Erath/Ground wire was not connected and that's a serious safety issue. For me a no go, so I fixed that. Please, do not disconnect earth from a metal hosing ! (IEC protection classes)
Like always in such restoration everything was cleaned properly (housing, switches, potentiometers, connectors, jacks, heads (demagnitized), bearings, pinch roller, ... bad solderjoints reflowed...
A new tape loop was installed.
A lot of work, but quite worth it. It is a great sounding chorus/reverb/echo.
Calibration was also performed on this beauty.
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!