Roland Juno-106 — Full Voice Chip Set & Factory Calibration (Plus Three Pedals)

Symptom

A Juno-106 in for a complete voice chip replacement, plus three pedals on the same visit: a Keeley Loomer with a footswitch dented in and broken, a Ross Chorus that buzzed on external power, and a Cooper FX Gen Loss whose buttons kept sticking.

Diagnosis

Juno-106: all six original voice chips replaced as a complete set with Borish Electronics replacements rather than swapping individual voices. The surviving originals are the same age under the same stress and follow shortly behind the first failure.
Ross Chorus: the buzz on external power was not the pedal. The 1/8" dongle I first tried was wired backwards for this pedal, and that is what produced the buzz. Separately, the supply that came in with it is labeled 9V but measures 12V at the output — too high for this pedal, and worth knowing before it gets used on anything else.
Cooper FX Gen Loss: the PCB pushes into the enclosure and jams the buttons because there is no proper mount point on the board. It had been glued at the factory, and the glue had failed.
Keeley Loomer: footswitch dented in and mechanically broken.

Fix

Juno-106: six Borish Electronics voice chips installed, followed by a full factory calibration per Roland service notes — power supply rails, DCO CV offset, VCA bias, per-channel VCA offset, VCF resonance, VCA gain, VCF frequency and width across all six voices, noise level, PWM, chorus bias, and load offset.
Ross Chorus: made up a new 1/8" dongle with the correct polarity, and sent the pedal home with a fresh battery and a regulated 9V supply so it runs on a normal pedalboard setup.
Cooper FX Gen Loss: re-glued the PCB and added a small foam spacer to keep it from pushing into the enclosure again.
Keeley Loomer: footswitch replaced.

What I Took Away

Replace Juno-106 voice chips as a full set. The original 80017A modules fail from the same cause at the same rate, so a unit that has lost one is not far from losing the rest — and the calibration has to be redone afterward either way.
The Ross Chorus is the useful one. A pedal that buzzes on external power but behaves on a battery is a supply problem, not a pedal problem. The two things to check before opening anything up are the polarity of the adapter and the actual voltage at its output. A supply labeled 9V that measures 12V will make a lot of pedals misbehave and can damage some of them.
No mount point on a PCB is a design problem, not a fault. Glue is the manufacturer's answer and glue fails; a foam spacer bearing against the enclosure holds better than more glue.