Repair AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

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Repair AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

This AMS DMX 15-80S Vintage Stereo Digital Delay was sent to me for repair in a non working condition. The first problem I encountered was a malfunctioning fuse. If I measured the fuse it measured continuity. But the AMS still didn’t work. But every attempt pointed me to the fuse. So finally I broke the fuse to have a look inside. I my mind there was a lot of corrosion going on which passed the test of a meter but not the 4+amp of the 5V rail.

Corroded Fuse of a AMS DMX 15-80S Vintage Stereo Digital Delay
Corroded Fuse of a AMS DMX 15-80S Vintage Stereo Digital Delay

Main reason for the non working condition and blown fuse seemed to be an exploded tantal capacitor. Now looks a bit like a black muffin.

AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

Next I encountered some heavy leaking electrolytic capacitors. Customer wanted me to re-cap the whole AMS and replace some edge connectors.

AMS DMX 15-80S Vintage Stereo Digital Delay from 1978

The MOSFET of the 5V rail got quite hot. After replacing the MOSFET, Re-Cap the whole AMS, I also renewed all heatsink compount and the mica. I also cleaned the potentiometer.

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.
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