Repair Roland Jupiter 4 Analog Synthesizer Reparatur Service

15. April 2020

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Repair Roland Jupiter 4 Analog Synthesizer Reparatur Service

Roland Jupiter 4 full restortion. The overall condition was not the best. When I did the initial test and switched it on for the first time one of the fuses on the psu blew up after a minute or so. So, let`s start doing this project.

First thing I did was to find out, what made the fuse blew up on the first test. Well, it was "just" a bad rectifier. After replacing that rectifier I did a full test with a load and the psu was in good condition. Since it looked all original I decided to do a full re-cap job. Not only on the psu, but starting here.

There was still the original battery inside, which was, of course, totally empty and, of course, leaky. I cutted it out and cleaned the area.

The battery always makes the same damage. Not only around the battery itself, but also corrosion was going up and under the main circuit board. I fixed the corrosion issue and put it a new battery with holder, so it can be replaced after three years. I also bypassed the charging circuit.

It´s not broken, so why re-cap? Because these old electrolytic capacitors are rated for a few years only and they intend to leak or they already do or did. Like in this picture you can clearly see the dark spots aound the capacitor holes. A bit more time passing by they will harm your synthesizer if not already happened. You can also see the electrolyte coming out of the capacitors like shown here many many times before.

Everything was corroded from moisture. Inside, some wood (!), some metal framing, but also all (front) panel didn't look to goo as you can see here.

I could clean all the moisture, corrosion and residue from the panels and they look very nice and shiny again.

Another good example was the shabby back/jack panel which rellay suffered from moisture and corrosion but...

but has now a good cleaning and looks almost like new again.

So after replacing a rectifier in the psu, re-capped the whole synth, replaced the batteries, refurbished all sliders, potentiometers, switches, key-contacts, keyboard, jacks, trimmers, a calibration procedure, took care about cosmetic issues (something missing?) the jupiter now is in great shape. It sounds bombastic and acts like new.

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!