Roland E68 keyboard intermittent sound

Hi. I have a Roland E68 keyboard, which has velocity sensitive keys (this may or may not be relevant). It all works fine when played softly, but as soon as any key is hit with more force, the sound cuts out intermittently (so it sounds like Morse Code) and continues to do so until the key is released. It affects all notes equally and whilst one note is 'on the blink', any other note that is played, regardless of how hard, 'blinks' as well.

The fault seems to fluctuate in severity - I have just tried it now and, for the problem to arise, I had to whack the keys harder than I ever would when playing for real, but yesterday it was happening just with normal 'expressive' playing.

Has anyone encountered this problem with this or any other model of keyboard? Does anyone have any suggestions for a diagnosis or solution? Any help would be greatly appreciated.

 

Update: I have discovered that it does not affect all keys equally - certain keys are much more prone to it (although whilst the affected key is held down, it still affects all other notes). Could it be a cleaning issue?

 

The velocity-sensitivity is derived from detecting the speed at which a contact closes therefore your assumption that some cleaning may be required seems quite valid.

Such contacts are often made from phosphor-bronze (potentially gold-plated) wires so any cleaning must be done with regard to getting the muck off but not destroying the plating....

 

Thanks for your reply. Do you have any tips on how to do that? I assume it rules out anything acidic - and water is probably not a good idea - but acetone? alcohol? switch cleaner?

 

Alcohol - specifically IPA (Isopropylalcohol) widely available. Small aerosols of 'quality' contact cleaning solution are also available. Check out electronics suppliers for such.

 

Thanks very much.

 

I have a Roland E-68 built in 1996 by Roland, that was completely cleaned out and serviced.

When I restored this instrument, I used only alcohol on the contact board underneath the key bed, using several Q tips while cleaning.

The contact strips ( see photo ) I soaked in lukewarm water with couple of drops of dish washing detergent. I also used a painter's brush and gently brushed each contact strip on both sides.

You don't have to go crazy on them, just gently remove the dirt, dust, oil, coffee spills or any residue that can be found on them. Once done, rinse them with water, and let them dry. I even used a hair dryer.

Once dry inspect the rubber strips, make sure no dirt or water is left inside the holes. Use a magnifying glass. If things look good, install back everything.

However; sometimes a cleaning doesn't always solve velocity issues, but it's the first step in eliminating any problems.

I'm glad to know that there are other E-68 users out there. Happy Keyboarding . Roland Rocks!

 

That's brilliant, Alektron. Thanks for your detailed reply.

 

Your Welcome.

One more thing. Make yourself a little installation tool for the contact strips. Find a paper clip that fits the holes in diameter, I'm talking about the tiny holes that go thru the contact board (they are on the edge of the rubber strip), they secure the right position for the strip.

Locate a paper clip that has a coating on it (plastic or rubber), remove the coating just deep enough so the metal won't poke thru the strip. Also make sure the metal is not very sharp on the end of the paper clip, and use this to press the strip thru the board. It's gonna be a breeze with this. Otherwise I think it would be a nightmare.

But remember! Be gentle, don't force it, if it's not going in look at it, why it's not going?!

You'll get the hang of it eventually...

 

The symptoms suggest a fractured solder joint or PCB trace on some common bus feeding all keys. It's more likely to occur in an area where the PCB is poorly supported and thus capable of more flexure than other areas.

If this is the problem, it will be difficult to spot visually. Use good lighting and magnification. If the unit can be safely powered while open, you may be able to locate the intermittent using gentle pressure from an insulated probe such as a bamboo skewer.

The problem can also be caused by a loose or defective connector.

 

I've stripped it down and given it a general clean - just waiting on delivery of isoprop for cleaning the contacts. If the problem persists I'll have to start looking deeper - but a good clean can't do any harm anyway.

KJ6EAD - thanks for the tips.

Alektron - The paperclip trick works a treat (I found one the right size first time!).

 

...I've cleaned all the contacts and put everything back together but the problem has not gone away.

I have, however, gained a bit more insight: the intermittent sound hardly happens at all when the volume is turned down very low, and happens more frequently when several notes are played at once, so it would seem to be related to signal level - and, importantly, it doesn't happen when the keyboard is plugged into an external amp from the line out or when using headphones. So it seems that the problem must be at the output stage and, since both channels are affected exactly the same, it is unlikely to be the speakers themselves - but that's about as far as my diagnostic skills will take me. What would cause both channels to cut out when the signal goes over a certain level, but affect only the built-in speakers?

 

This still sounds like a mechanical flakey on the PCB, but somewhere in the output path to the speakers, probably the last amplifier stage since all others are likely to be in common with the symptom-free modes.

To address your specific question; if the problem is a component failure, electrolytic capacitors are always a high failure item but diodes, transistors and op amps can also act in a threshold sensitive manner. A weak power supply can also cause the effects you're seeing. Pictures of the board and schematics would be useful at this point.