[sdiy] SL880 Pro problems

[Brian Willoughby]

On Nov 6, 2021, at 14:04, Mike Kelly <mike at downlode.uk.net> wrote:
> Hi, I wondered if anyone has experience in troubleshooting Studiologic SL880 midi keyboards. I picked up this one second hand and really like the weighted action.
> Since the off there has been a problem with some rogue midi output signals. Plugging a volume pedal into the volume socket seemed to solve it. Now however after a couple of years of use I am getting random and unstable outputs and it’s unusable. I tried changing a couple of the electrolytic caps as I had spares. The board generally looks OK and the settings functionality and the LEDs all seem to be working fine, so I think there’s not much wrong with it. If anyone knows a likely point of failure on these boards please give me a shout.

You could probably also buy a 1/4" jack and wire it like a volume pedal fixed at the maximum. You're probably picking up noise on the pedal input when nothing is plugged in, because the Studiologic company did not design the case and/or circuit correctly to handle that input.

Now that you've replaced a couple of electrolytic caps, it's entirely possible that you've created new problems. It's never a good idea to do amateur repairs on your favorite instrument. The risk is just too high.

What sorts of "random and unstable outputs" are you experiencing? I assume that this is a pure controller with no audio, so the only output should be MIDI. I'm not sure what "unstable" would mean in this context.

> I thought about replacing the crystal as it looks a bit aged. Marking is 24.0MHz, HCJ-30 02-02-57. Would any 24MHz crystal do? Or am I on the wrong track.

You're definitely on the wrong track. Crystals do not fail partially. The fact that your controller is working at all means that the crystal is fine.

You absolutely should not continue to replace parts without proof of what is actually wrong. Every change introduces more potential points of failure.

> Alternatively if there’s a way to put a whole new DIY circuit in there I could go that route. They’re Fatar keys I believe, with aftertouch.

It's unlikely that a DIY circuit would perform better than the original design. If there's something wrong with the original design, then the problem is most likely in the case itself - shielding from noise (i.e. random and unstable) - and putting a different circuit in the same box won't help. Your story about the volume pedal input flakiness tells me that Studiologic did not design a reliable product, and the cheap design - especially mechanical aspects like quality, shielding casing - will surely hold over even if you replace the guts.

> Thanks.
> M

Sorry for the bad news. Take your favorite controller to a professional.

Brian Willoughby