Sunday, March 5, 2017

Juno-6 with trigger problems and broken switch

A Juno-6 with a couple of minor issues

So my second repair was a Roland Juno-6 that had a couple of minor issues.

Trigger heard on output

One of them was that the trigger signal connected to the trigger input (for clocking the arpeggiator) could be heard on the output.
I figured it must be some audio input modification so I opened it up to have a look.

Here's what I could see.
That gray cable is not original
From the arp trigger input jack there was a gray cable going to the rightmost panel board via a capacitor and resistor.
The cable was soldered to the pins of the arp trigger input jack. Furthermore the PCB traces leading from it were cut.
There's your problem!
So it immediately became obvious someone wanted to use the trigger input jack for something other than triggering, since those traces were cut. So where was the cable connected in the other end?

I did a quick check and, without giving it too much thought, I realized the resistor and capacitor is just an AC coupling for an audio signal to allow it to be injected into the audio path somewhere.
I don't remember exactly where it was soldered in, but it was somewhere after the VCF section.
Though I guess you could figure it out from the first photo if you want, but it's not really important.
I was now convinced this was just an external audio-in mod to allow an external signal to be processed through the Juno chorus.

The important thing was to get it working properly again.
Luckily it was a simple task; just remove the gray cable with the cap and resistor and patch the two cut traces on the PCB to restore connection of the trigger signal to the arpeggiator circuitry.
After doing that, I tested it and it worked just fine, so that was a quick fix!

Broken VCA switch

The second issue with this Juno-6 was that the VCA Env switch was broken.
I had a few replacement switches so after replacing the broken switch, it was once again possible to switch between Gate and Env mode.

All done! Fast and easy. :)

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