Vintage Synth Explorer Forums

Hello,
I just bought an Ensoniq SD-1 or to be precise a VFX-SD with a SD-1 mainboard (changed by customer service in the 90s). At first it seemed it works well, but then I noticed crackling noises, mostly when playing Bass patches. The crackle sounds like dust on a vinyl record. Sometimes it isn't there from the start, it seems that I trigger it, when pushing the keys in high velocity. When crackling is present, it stays also on sustaining notes so they really sound as if there is a vinyl fx going on.
I already changed OS Eeproms from 3.00 to 4.10 with no improvement.
The heat sink is also getting very hot, so perhaps there's a PSU problem? Worn out caps?

Hello,
I bought an ensoniq VFX long time ago and I had a similar problem.
Some of the patches had a noisy that came from the FX of the synth, from REVERB effect to be more specific.
Try to look there, increasing and decreasing the volumes .
I don't know the reason that causes this, but but mine I could solve if I turn off the FX.
Sorry for my poor English but hope it helps.

Thanks for your reply. On mine it doesn't seem to come from the fx section.
Yesterday I plugged the SD-1 into the line input of my audio interface instead of the guitar amp I was using before, and there weren't any problems. So I think the crackle is perhaps caused by wrong input impedance (I'm so dumb ).
But now I noticed that the data slider is changing values by itself, and on midiox I see random pitch wheel actions.
In that vfx sd repair thread there was mentioned, that this could be caused by ripple current on the 12V rails; so what do I have to change to fix this?

n'sonq wrote:But now I noticed that the data slider is changing values by itself, and on midiox I see random pitch wheel actions.

In that vfx sd repair thread there was mentioned, that this could be caused by ripple current on the 12V rails; so what do I have to change to fix this?

Rebuild the PSU. Specifically, the caps that are involved in the -12/+12 analog rails. But, in my opinion, if you're going to do that, you might as well just replace all the electrolytic caps on the PSU at the same time.

This page lists the caps and their modern replacements: http://zine.r-massive.com/recapping-cla ... -samplers/

Thanks for the link. I will recap the psu and mainboard soon and also change all voltage regulators.
Meanwhile I encountered more problems. When the SD-1 is running for some time, it randomly reboots itself multiple times, sometimes with error messages 137 and 144 in-between.
Reference voltage value on the analog test page is near 100, so I guess this behaviour is indeed psu related.