MIDI Keyboard Controller issue

FatBoy

As discussed in this thread http://www.guitarforum.co.za/guitar-gear/midi-controllers-the-good-the-bad-and-the-ugly/ I have an issue with one of the keys on my controller, it is an Edirol PC-300 by the way.

Problem is this, the keys are velocity sensitive, meaning if you press it softly, the sound is soft. Press it down hard and the sound is loud.

One of the keys (the middle one of the 5 that has the keys taken off) does not register the keypress if I press it softly, but works when I hit it real hard.

I opened it up, took the keys off and found this

If I press down on the white rubber thingies it works perfectly, soft or hard etc. I have tried using a different key in that position and had the same issue. Tried using the key that had the problem on another white rubber thingy and it works perfectly.

Have removed all ribbon cables and plugged back in an no change. Tried fiddling with the rubber thingies to see if it's loose or something and no luck. I checked for loose soldering etc and I can see none, but I have no experience of electronics so I might be overlooking something.

I am really stumped here, any other ideas guys?

Manfred-Klose

Isn't there something in the rubber thingy that blocks the key perhaps?

Try moving the rubber downwards a little, very little, not even a millimeter.
The one rubber kind of looks out of place if you look closely

AlanRatcliffe

I've fixed my keyboards sucessfully a few times when they've done this (and countless older computer keyboards that had the same system). Most likely it's a bit of dirt under the rubber or on the circuit traces that the conductive bit on the end of the rubber shorts to make contact. Lift up the rubber and wipe it and the traces with a soft, clean, dry cloth and put back together. If that doesn't work, wipe the traces with isopropyl alcohol and allow to dry thoroughly before you put the rubber back. That should do it

FatBoy

I fiddled some more tonight (mostly just moving the rubber thingy around and wishing it would work) and it is a lot better, still not 100% though.

The keyboard was kind of dusty when I got it, so yea it could well be dirt.

It looks like all the rubber thingies are attached to each other in one long strip. I'm kind of scared to take the whole thing off, with my luck it could easily screw up some of the other keys too. Do you normally take the whole thing off or just lift up enough to get to the problem area?

I will take a few days to build up the courage to do this and then report back!

AlanRatcliffe

Do you normally take the whole thing off or just lift up enough to get to the problem area?

I haven't worked on a PC-300 before, but the whole thing should just lift up as one. There will likely be locater pins on the rubber and corresponding holes in the PC board to line it up and get it all back together in the right place.

The keyboards I've worked on, access is usually from the back rather than under the keys - the back comes of, the board unscrews and lifts up and the rubber pads are underneath. The newer ones all have a contact sheet rather than a PC board.

FatBoy

Ok cool thanks, yea I have seen the locater pin thingies, will give it a try.