Roland Alpha Juno 2

Mod-wheel / bender

mod-wheel assembly with hexagon screw in the middle

If the mod-wheel has no hearable effect, but is movable and snapping towards the middle, the small black hexagon screw is eventually not tightened. Just tighten that screw and test the bender again.

If then the bender has a hearable effect, but gets stuck or moves to its middle very slowly, the cause can be a stuck axis of the pot. To solve this, open the hexagon screw again, and also other screws so you can disassemble the bender parts. Put a suitable contact spray (I've used WD40) onto the axis of the pot. Turn the axis a minute or so back and forth until it's getting at least a bit more movable. After some hours the contact spray will become even more distributed by itself between the axis and the pot housing, now the pot will be easy movable.

The forward-pressing feature of the bender can also do just nothing anymore: There is a small pressure sensor in the mod-wheel assembly. The piece of ribbon laying inside seems to lose it's ability for appropriate conduction over time and has to be replaced. It is taking apart in the following two pictures:

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  conductive ribbon of pressure sensor

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  contact foil with ribbon removed

Stuck Alpha-dial

If the Alpha-dial is difficult to move, it also needs contact spray onto the axis of the pot, and a minute or so of moving it. After some hours later it will move totally soft again.

Alpha-dial with cover removed

Leaked caps

In my case, there was cracking sound and suddenly no sound at all, because of leaked caps C11 and C12: They damaged the conductor beneath. Remove the faulty caps, check the conductor, and replace the caps with same capacity and same voltage or higher voltage.

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  leaked caps

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  removed caps showing damaged conductor

Aftertouch: Replacing the pressure sensor

If the aftertouch isn't working anymore, the pressure sensor under the keys may be broken. This one is quite a lot of work: First you need a suitable spare part. I couldn't find a sensor that was long enough. So I've used two "SF15-600" pressure sensors connected together with two small strips of self-adhesive copper-foil and kapton-tape:

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  one SF15-600 with copper foil half assembled

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  two SF15-600 pressure sensors with copper foil assembled

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  assembled view from back

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  new pressure sensor mounted under keys

The resistor value of this one feels just right to me for the aftertouch. You can test your sensor first by plugging it in, before removing any keys and the old sensor. It is connected at the small PCB with the 2-pole connector.

If the aftertouch works, the sensor can be put in place: Remove all keys (good opportunity to clean them), remove the white fleece strap, remove the old pressure sensor, glue the new tested one in place, put the fleece strap back on and put on the keys again.