One for the Experts! Crazy Ebay Roland MKS-30. Please Help!!!!!

[David Perry]

Hey guys,

 

What follows is a bizarre acount of what is probably a very esoteric electronic problem with a classic DCO synth which I was unfortunate enough to have just bought. Any technical synth experts with advice---I'd REALLY be grateful for any help you can give on this one...

 

Today I'm and kind of , because I just got a Roland MKS-30 in the mail I paid $250 for and from first power up it was not functioning correctly. I've emailed the seller but so far no response.

 

Here's the deal: powers up fine, all connections seem fine, midi receive light lights for every note I play on my controller, BUT, notes don't sound consistently. Biggest problem, a fluxuating group of notes (always two notes per octave) doesn't sound at all, or there is a very faint thumping when I hit the key and nothing else.

 

Okay, here's the weird part:

 

The non-sounding notes change in a very consistent way. If I play a run up and then back down, the same notes fail to sound. But if I play any chromatic run up and then up again, or down and then down again, the non-sounding notes change, and they change in consistent groups. To make things weirder, it also will happen if I play any non-chromatic scale in the same manner as above, but only if it's a full octave. If the up/up or down/down run is chromatic, it can be less than an octave and the non-sounding group will change, but otherwise it will keep staying the same.

 

The notes are always in the same groups of two, though the appearance of the pairs does not cycle through and begin again. The order of the pairs appearing seems random now, but there may be some larger pattern. The non-sounding pairs are always:

 

E flat & A

C & F sharp

F & B

D & A flat

C# & G

E & B flat

 

As you can see, these notes are always six semitones apart, or a tritone. In other words, they are always notes that are not in each other's keys.

 

It never deviates from these pairings, but, as I said, at this point it seems to cycle through the pairs randomly each time I start an octave or chromatic fragment again from the top, or again from the bottom, but not when I alternate ascending/descending.

 

Another thing it's started doing is seeming to apply vibrato or an LFO randomly to some notes, but that has only happened on one program I think and I'm far less concerned about that (obviously). If I could just fix this primary problem at not great expense of hassle it would make keeping the synth a possibility.

 

He stated in the ad it was functioning properly, but who knows. One thing for sure is it was packed extremely well with tons of bubble wrap and paking peanuts in an oversized box. There was no visible damage to the box whatsoever. The module itself is cosmetically in good condition, with no visible serious damage.

 

Once again, the midi receive lights on every note, and my controller indicates midi sent on every note, and I haven't had this problem with other modules.

 

Anyone with technical knowledge of synths please offer any diagnosis and/or advice you can. I like this synth and it's fun to program because I have the PG-200 with it, plus I'd really rather avoid any problems with the seller so a relatively easy fix would be a most pleasant thing to discover.

 

Thanks so much in advance!!

 

David Perry

Corvallis, Oregon

[synthetic]

I was going to suggest reinitializing the synth, but a quick web search told me there isn't a user reset on that product. Is it a 6 or 12 voice synth? It sounds like one of the oscillators and/or filters is messed up. With voice stealing that would make every 6th note mess up when playing a chromatic scale. In that case you would probably have to take it to Roland for service, sorry. Or maybe a shop that repairs vintage Roland gear.

[David Perry]

Hey, thanks, I appreciate your response. It is six voice, but both oscillators (2 per voice) are affected for every note, and it doesn't simply affect every sixth note (I realize my explanation is complicated). If I start a chromatic scale on C it has been C and F# that were missing, then when I would start over with C, it would then change to F and B that were missing, etc. etc., so it's not a repetitive number like every sixth note. The only thing that is repetitive is that there are always pairs of notes missing from each octave, and they are always a tritone apart.

 

I know, very strange and frustrating! Thanks for your help!

 

Dave

[BP3]

I had a similar thing happen with my Matrix 6R. One of the six voices would occasionally flake on me.

 

I opened the Matrix and found that it had a chip for each oscillator. One of the chips had loosened from it's socket. Once it was re-seated, everything worked fine. Perhaps the Roland is built in a similar fashion.

[David Perry]

Hey, thanks everyone for your replies!

 

I'm pretty sure synthetic is actually right. I now feel like I've narrowed the problem down to simply one of the six voices being dead. Based on the voice allocation for different key sequences it's a little confusing, but I think the giveaway is that whenever I play chromatic scales it's always the sixth note that I play that is gone, no matter where I start on the keyboard. There's no way to know what part of the voice has gone bad, but it is affecting both oscillators. Incidentally, I've heard the dead voice try to kick in two or three times along with a thumping noise like the amp suddenly getting some kind of signal or trying to kick in, but then the voice dies away in about a second. This has only happened a couple times in hundreds of keystrokes, though. I suppose it may mean the problem is with the VCA for that voice but who knows. It's definitely going to require service from a qualified person with acces to some of these older components and the equipment required to test the IC's, etc.

 

Can anyone tell me who or where to inquire with about how much a fix might be?

 

Thanks again,

Dave