Bad JP8 envelope slider

The Roland Jupiter-8 Analogue Synthesizer
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December Agents
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Joined: Sun Jul 20, 2014 4:32 pm
Location: Chicago

Bad JP8 envelope slider

Postby December Agents » Fri Mar 04, 2016 4:46 pm

The ENV1 decay slider on my Jupiter-8 has a problem: It seems to kick in and work a little bit when its setting is near zero decay (at the bottom), but is ignored as though out-of-circuit when the wiper is in any other position. It does this even when the slider pot is taken off the PCB and connected to an ohmmeter, so the problem is definitely in the slider and not elsewhere.

As you probably know, the finding replacement parts for this is like finding the fossilized remains of a previously unknown dinosaur species. For what it's worth, it is Roland part number 13339415, which is a 10k linear slider pot. It is the same pot used for most of the sliders on the JP8 front panel. Anecdotes of people finding them are like the tales of Beowulf and King Arthur -- you hear of it now and again, but it's the stuff of legend. (But I'll certainly take any leads to a source if anyone has one...)

However, unless someone actually knows of a replacement, it looks like my only hope is to repair the existing slider. Simple cleaning has been tried. To me, it almost seems like there's a break in the carbon track, or at least that would seem to explain the behavior of working at one end and then being inoperable everywhere else.

Is there anyone who can fix a thing like this, or tell me what I should do? It's a Jupiter-8 with Encore midi and no other problems. It shouldn't be allowed to die and become useless over one 10k slider pot.

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