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Dead Roland JUNO-6

Posted: Tue Nov 10, 2015 6:39 pm
by HaziaJuno
Hey all! New to the forum, I'll try my best to observe the etiquette! :)

I'm here on account of a Roland JUNO-6 that has made it's way to me.

It is in really excellent cosmetic condition, it is complete with no missing parts, and everything looks to be in great shape.

But functionally - something is very wrong. Let me disclose - when it comes to service/electronics work, my knowledge is basic at best.

The keys do not respond. There is a strange sort of hum, a constant tone in the background, which becomes more pronounced when the choruses are switched on. Also, the key transpose button does not seem to illuminate or respond (thus hindering my ability to put the instrument in "test mode").

I opened it up and tried cleaning the key contacts and busbars, and that wasn't the problem. I scanned the boards looking for signs of bulged/leaky capacitors - nothing stands out. I tried fussing with the "L-M-H" level switch (already fixed a JX-8P by trying this) - all to no avail.

The seller very openly sold it as a "non-working" instrument, and had posted this video of it's functional condition:
https://www.youtube.com/watch?v=MwFRDnfIm54

I live in Anchorage, Alaska, and my options for shops that service vintage instruments is nil. I am determined to repair this beautiful old thing - but I need help!! I love the Juno-6 so much, and any recommendations would be welcome, whether it be help in assessing/diagnosing the problem, or even recommendations on synth techs that will accept instruments from out of state.

Thanks, all!

Re: Dead Roland JUNO-6

Posted: Tue Nov 10, 2015 9:06 pm
by sam
first stop is to find the service manal and check the voltages going to the boards.

Re: Dead Roland JUNO-6

Posted: Tue Nov 10, 2015 9:31 pm
by HaziaJuno
sam wrote:first stop is to find the service manal and check the voltages going to the boards.
I did manage to find a copy of the service manual, and I just bought a cheap meter a while back - but... I'm not really sure what to check. Or where. I really am quite inexperienced at this. :oops:

Re: Dead Roland JUNO-6

Posted: Wed Nov 11, 2015 12:25 pm
by madtheory
My opinion: the Juno 6 is worth a lot these days, upwards of €800 now if I'm not mistaken? If you're not experienced, it's worth the investment to send it to a tech. Alternatively, buy "Electronics for Dummies" (it's actually pretty good for beginners to learn from) and do some of the projects in that before you tackle a valuable polysynth.

That said, if the hum is indeed a hum, it's likely something's up in the rectifier area, most likely the smoothing caps. However, if it's more of a buzz, then it's a ground loop or open circuit in the audio path, which is much harder to diagnose. But realistically we'd need more info about the fault to make an accurate diagnosis.

Re: Dead Roland JUNO-6

Posted: Wed Nov 11, 2015 7:10 pm
by HaziaJuno
madtheory wrote:My opinion: the Juno 6 is worth a lot these days, upwards of €800 now if I'm not mistaken? If you're not experienced, it's worth the investment to send it to a tech. Alternatively, buy "Electronics for Dummies" (it's actually pretty good for beginners to learn from) and do some of the projects in that before you tackle a valuable polysynth.

That said, if the hum is indeed a hum, it's likely something's up in the rectifier area, most likely the smoothing caps. However, if it's more of a buzz, then it's a ground loop or open circuit in the audio path, which is much harder to diagnose. But realistically we'd need more info about the fault to make an accurate diagnosis.
It is definitely more of a hum... well, really more just like one or two continuously sustained notes. They get gradually louder, and I can apply the chorus effects to them, and they are affected by the HPF, noise, pitch bend, LFO sub octave, and resonance.

They are unaffected by the VCF frequency, PWM, ADSR, and... well, virtually everything else, really.

The completely non-functional key transpose raises some questions - I even tried to bridge the connection manually with wires to diagnose a possible failed momentary switch, and even then it failed to illuminate/function.

At this point, I've pretty much done everything I'm experienced enough to do. FUBAR or not, I care WAYYY too much about this instrument to risk damaging it further. All I can really do now is find a tech to ship it to...

I'll check out that book, though. Never a bad time to learn more.