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Juno 106 chip revival


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I've mentioned before that I recently replaced a few of the infamous chips in my 106 from a donor and shortly thereafter another voice decided to act up. Today I decided to try that trick about removing the coating on the chip to see if that revives it.

 

I removed the problem chip this evening and presently it's soaking in a bath of acetone. I'll post updates and pics here and let you know if it's really a viable solution!

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That's what's been thought. This isn't my idea, someone else had posted this a few months back. I couldn't find the thread, though.

 

Hey, if it works, then WOOT, 'cause while warming up the Juno to find the bad voice, ANOTHER voice started freaking out with resonance.

 

Ugh. I think my Juno just wants to go quietly into the night. :cry: (or not-so-quietly, really.)

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How much do new chips cost?

 

I know a guy who has a 106 that he hasn't used in 20 years. I've always wanted to buy it from him but knowing that they're all dying doesn't exactly put a flame under my butt to wheel and deal. It's there when/if I want it, I suppose. Also, who's the source for new chips?

 

One of the holes in my arsenal is a true analogue polysynth. The 106 would kind of fill that hole. A dual oscillator per voice poly would be ideal. But at this point, they're double the problems and double the expense. No way I'd pay a couple grand for a vintage Prophet, Oberheim, or Jupiter with their voice cards and chips dying. Especially when I just get off on making ELO sounds.

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Thermally overloaded. Put heat sinks and thermal transfer materials and some active cooling on the chips. They make clip on heatsinks. If removing the resin coating is helping the chips are overheating. Does anybody have schematics for these chips ?

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They were proprietary "chips" made up by Roland, and they never published detailed schematics for them. The service manual gives an overview of the design, so some enterprising individuals have managed to make clones, some closer in operation to the original than others.

 

I'm curious to see what's under the covers, too. We'll soon see.

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I hadn't heard about "metal particles" in the resin, but I had heard the "becoming conductive" angle. Someone suggested moisture as a culprit. Don't know if that's true or not. I'd also heard a theory about metal migration underneath. If that's true, then simply removing the resin won't help.

 

While I was waiting for the Juno to warm up so I could pinpoint the problem child, I copped a feel on the chips. They run warm, but not hot. Not sure how hot they will get if I just let it run.

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Yeah I'm not buying heat, either.

 

If it is accumulation of moisture, would just tossing them in the oven work for long? Perhaps the resin becomes more susceptable to moisture as they age and drying them out would be a short-term fix.

 

Maybe ought to try just putting the whole board int he oven for a while. :lol: I wonder what a maximum safe temperature would be...?

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As far as I know they use epoxy potting compounds for this kind of thing. Epoxy unlike catalised resins needs to be mixed accurately. IE if you add too much hardener it does not get harder quicker, you just end up with solid expoxy filled with unreacted excess hardener. The unreacted resin of these two part epoxy systems is corrosive, so if a manufacturer does rush and mess up the mix then it could cause problems. Cleaning off completely using accetone and scrubbing with a tooth brush would get rid of any conductive problem as the chap in the vid suggests.

 

One other effect with electronics is all the banging and handling done in such activity, it can also restore life to a circuit, albeit for a short time. Some car mechanics will give an electronic igintion module a sharp tap to get the thyristor to fire up and start a car in emergency.

 

Hopefully the problem is corrosion as that accetone bath will be a longer term fix.

 

Good luck

 

:wave:

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Wow, wish I knew about this trick a couple winters ago when I was refurbing a couple 106es.

 

It probably won't salvage every chip but even if it brings back 50% of them it's a nice cheap solution. And once the resin is off, one could touch up the solder joints to fix a failed chip as well.

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