Read enough Juno-106 listings and you'll see "voice chip" in half of them. It refers to the six 80017A chips inside, one for each voice. They're the Juno-106's best-known weak point, and they're why two 106s that look the same can be very different buys. The fault is well understood and replacements are made today, so a Juno-106 is still a fine first synth if you know what you're looking at.
What the 80017A is
Roland's part number is A1QH80017A, and very early ones are stamped 800170. It isn't a single chip. It's a small hybrid module, a collection of surface-mount parts on a tiny board, dipped in resin. Each one holds the voltage-controlled filter and amplifier for one voice. The filter is built around Roland's IR3109 filter chip, the same one Roland used directly in the Juno-60 and SH-101.
The oscillators live elsewhere. Three MC5534A wave generator chips make the waveforms, each shared by a pair of voices. That matters when you diagnose a fault, because a voice that's missing its sawtooth or square wave points to an MC5534A, not an 80017A.
The same 80017A was used in Roland's HS-60, the Juno-106 version with built-in speakers, and in the MKS-30 and MKS-7 rack modules and the GR-700 guitar synth. The Juno-60 doesn't have it.
Why they fail
The resin is the problem. Florian Anwander's notes on Roland filters say the chips are known to fail after about ten years. A Synthtopia repair feature says the coating Roland used begins to conduct electricity, and that causes the faults. Analogue Renaissance, which has made replacements since 2006, adds that the originals were built with ultra-thin traces and printed resistors. Roland no longer makes them and has no spares. The originals in any Juno-106 you buy are around 40 years old, so treat every one as on borrowed time.
The symptoms
Analogue Renaissance describes the most common problem as one or more voices going dead, or a voice that keeps sounding after you let go of the key. Its published test method, done from the synth's hidden test mode, sorts faults into groups.
- Constant noise with no key held: a VCA that's stuck open.
- One voice with no noise when the others have it: a dead VCA in that voice's 80017A.
- With resonance up, a voice silent or far off pitch: a failed filter in that voice's 80017A. If it's only a little off, the synth just needs adjusting.
- A voice that keeps whistling as you lower resonance after the others stop: a stuck VCA in the filter's feedback path.
- A voice with noise but no square, sawtooth or sub-oscillator: a failed MC5534A wave generator.
Some faults only show up warm. One Synthtopia reader's Juno dropped a voice after 30 to 45 minutes of playing. A short demo video can miss that, so a seller who has played the synth for an hour or more can tell you more than one who has only switched it on.
How to test a listing
Ask the seller for a video in test mode. It takes a minute.
- Hold KEY TRANSPOSE, switch the Juno-106 on, and let go. The display should show "-_".
- Press POLY 1 and POLY 2 together. The synth now plays its voices in rotation, and the display shows which voice is sounding.
- Turn the noise slider up and play several notes, so every voice gets a turn. Each should give the same noise.
- Turn noise off, switch on the square wave, then the sawtooth, then the sub-oscillator, playing a few notes each time.
- Turn every source off, set the filter cutoff to the middle and resonance to full, and play one key six times. You should hear six very similar whistles, and they should all fade at about the same point as you bring resonance down.
If the seller can't do that, ask at least for a video that plays one note six times with a plain sawtooth and the filter half open, and listen for a voice that's quieter, noisier or missing.
Replacement options
- Analogue Renaissance AR80017A. The current version of a clone first sold in May 2006. It isn't dipped in resin, and the maker says it matches the original's sound and is built to survive mistakes during installation. Syntaur in Texas is one of its distributors.
- AR80017A-GS. A deliberate upgrade from the same maker, built around a modified ladder filter. Analogue Renaissance describes the result as a bigger sound, so it's a different-sounding Juno. If a listing says "upgraded voice chips", ask which ones.
- Other makers' clones. Other clones have been sold over the years, and some are resin-dipped like the originals. Ask the seller for the brand.
- Used originals. Chips pulled from scrapped Juno-106s are the same age as the ones they replace and fail the same way.
- Reviving an original. Dissolving the resin coating with acetone brings some failed chips back. Synthtopia's source says it doesn't work in every case.
Fitting a chip isn't the whole job. Analogue Renaissance says the adjustment procedure in the Juno-106 service manual has to be done afterwards, even when the new chip is an original. That calls for a multimeter, an oscilloscope and a frequency counter or tuner. Analogue Renaissance says a Juno that skips this step sounds acceptable but not right.
Reading the listing
- "Voice chips replaced": ask how many, which brand, and whether the voices were adjusted afterwards. Six clones, fitted and adjusted, is the best case.
- "Needs a voice chip": plan as if the remaining originals will follow. Ask whether the seller has tried test mode to see which voice it is.
- "All six voices work": good, but it's only true today. Ask for the test-mode video anyway.
- HS-60: the same synth with speakers, and the same chips. Everything here applies.
Search results also turn up the Roland JU-06 and JU-06A, small digital Boutique modules, and the Behringer DeepMind, which was inspired by the 106. None of them uses 80017A chips, and none is a Juno-106.
Should you still buy one?
Yes. The Juno-106 has MIDI, 128 memories and a sound that's on a long list of records. The voice chip is a known cost, and you know the fix before you buy. A unit whose chips have already been replaced and adjusted saves you that job. One with original chips that all pass the test-mode video is fine too, as long as you expect to replace them in time.
If you're weighing the 106 against its rivals, read choosing a first vintage polysynth. For what a full service should include, see vintage synth service. For listing warning signs, see eBay seller red flags.
