Emergency Room #10: Juno-106 Acetone Treatment

“The essence of the beautiful is unity in variety.”

– Felix Mendelssohn –

Where there is art, there is beauty. And according to Felix, where there is beauty, there is variety. The audio electronics world is no exception. There are multitudes of audio effects out on the market, and the common differences they exhibit renders their design an art form all its own. This blog generally deals with audio effects equipment, but the diverse nature of the audio world prevents me from dealing solely with guitar effects repairs. Today we turn our attention to a popular synthesizer from 1984, the Roland Juno-106 Analog Polyphonic Synthesizer.

This thing is a BEAST! But these days, there’s a common problem that owners of these synths should look out for: the failure of the Roland AR80017 Voice Chips. Apparently this is a super common problem with these units, and if you’re here reading this you’re probably suspecting the voice chips to be the reason for your faulty Juno.

In order to isolate the problem to the voice chips you’ll have to utilize the Juno’s built-in troubleshooting method described in EXPLORING AUDIO’s YouTube video, “ROLAND JUNO 106 : VOICE CHIP ISSUES.” You can also find the procedure on page 18 in the Juno’s service manual, found here.

 

Once the problem is isolated to the Juno’s voice chips the procedure described by Jeroen Allaert of Analogue Rensaissance can be used to remove them. Allaert has done some remarkable work on the AR80017A voice chip; he’s even re-engineered a replica of it which can be purchased from his website. Another replica chip can be bought through ModularAddict.com as well. So even if the following procedure doesn’t do the trick, there are replacements available.

Once the chips are removed you can start the dissolving process! Fill a glass container with acetone (100% is best) and submerge the chips. Let that sit for 24-48 hours and check the condition of the outer epoxy resin cover. You can tell when the acetone has done its job by how disassociated the resin becomes. Gently peel off the larger chunks of resin and use a small tool (something similar to a precision flat-head screwdriver) for removing the smaller bits of resin left behind.

The reason acetone is used is because its a solvent for plastics (rubbers, polyethylene, etc.). It does a great job at breaking down polymers, and the epoxy resin encasing the voice chip is a decent candidate for the dissolving reaction. In fact, excess glue can also be removed using this method.

Once most of the resin is removed you can solder them back into the board. A good pair of helping hands or something to prop the board on its side is essential in order to easily solder the chips back into place. Solder one pin to support the chip on the board, then solder the rest of the pins with relative ease.

That’s it! Thanks for visiting Mimmotronics, please follow the Instagram and Facebook pages if you liked the post. Stay tuned!


This post was done as a result of working with Cody Morse, guitarist for Buffalo, NY, psych-rock band Deadwolf. on his faulty Juno-106 synthesizer. See their feature in the Buffalo internet TV show, the Attic: