Roland MC303 restoration

Hello everybody,

I recently bought this groovebox to have a first experience of restoring old material. I’m a bit lost to know what to do. Here is the list of issues:

  • The white ‘‘piano’’ buttons are yellow, and there are 3 buttons that don’t hold, move left, right, up, down and forward.
  • The button of the envelope moves a lot, up and down,
  • The low boost knob is very very sensitive. Sometimes I don’t hear the kick, and I just hit that button a little bit and it’s fine. Too sensitive and lots of crackles when I touch it
  • The machine makes a lot of breath, old circuits I think…

So if you have any advice, a tutorial link to solve this problem, a product reference that I need, it will be very useful.

Thank you so much!

Get yourself a copy of the manuals. I found a copy of the Service notes on manualslib by doing a search for ‘roland mc303 service manual.’ In the service notes you will find instructions for accessing the test mode beginning on page 7.

I don’t have one of these to look at, but the buttons Roland uses are typically a plastic button that makes contact with a switch mounted on the circuit board. Excessive/unusual travel might indicate that the plastic on these buttons may be broken.

I’ve seen a lot of failure in the switches that Roland uses. Over time, they just fail and won’t make contact unless you press harder and wiggle the button. The only practical solution is to replace these buttons - even the ones that seem to work now.

Likewise, the potentiometers used in the controls will get scratchy if they haven’t been used for long periods of time. You may be able to clear them up by exercising them, but I would replace them if possible for reliability.

It may be possible to de-yellow the white buttons. Look up ‘Retro-Bright.’ I haven’t done this myself, but you apply a peroxide to the surface of the plastic and leave it set in the sun for a period of time based on how discolored the plastic is. The results can be impressive.

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Thanks a lot for your reply, I gonna do a post when I finish this project