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patching out a Roland SH-3a?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author patching out a Roland SH-3a?
thetwlo
any tips/guides? it seems like an obvious thing. And seems like the perfect thing for this, but the A.Sol. reviews of their conversion aren't so positive. Is it that difficult? seems like this sounds great, and are usually cheap.
I wish I knew this stuff, as a patchable daughter board should be easy. No?
Inspired by they ebay post on the silly modular. The SH-3a really does sound fantastic. Already has a lot of CV, but lets make it fully patchable!
scozbor
Check the DIY section i think. A dude in sydney is doing a full rebuild with extensive mods for patching etc. He is hopefully doing mine next!
thetwlo
scozbor wrote:
Check the DIY section i think. A dude in sydney is doing a full rebuild with extensive mods for patching etc. He is hopefully doing mine next!

i thought this was the "DIY section" ? no? cool! but is it that hard to diy yourself? just feel there's enough out there, that a proper daughter board would be worth it.
home_listening
This is what is possible, I haven't had a chance to work on anything for months though. All of this has been tested on the bench but not implemented per se.

VCO CV in
VCF CV in
LFO1 rate CV in (using a vactrol, I haven't tried this before so lets see)
LFO2 rate CV in (as above)
VCF res CV in (as above)
Gate in
ADSR out
LFO2 saw out
LFO2 sine out
LFO1 saw out
LFO1 inverted saw
Noise out
Keyboard CV out
Keyboard Gate out
S+H out
S+H clock/sample point in
VCA audio in

It is painful because the metal panel with the controls (other than being completely full for the most part) is a sheets of thick zinc plated steel and another steel panel. The painful part with the other panel with the music stand is there is plenty of emi bleed from the psu (I put a decent sized toroid and new psu in mine). Was going to do a db-25 breakout box with buffers etc in it, but just haven't had any time.

You are right though, the board is a great one. 5 lfo's, plenty of CV everywhere. I think I'm going to put it behind a serge style panel and cut up the keyboard to use as a CV controller. But I feel bad butchering...
scozbor
Please keep us posted home_listening
Even half of those mods would be amazing. SlayerBadger!
home_listening
OK, had this almost done for a while thought I may as well take some photos. Please excuse the crappy quality, my DSLR isn't around at the moment. As you can see I added the patch points above the keyboard. I also added LED indication for the envelope and LFO outputs. So I patched out 3 of the LFO outputs, all four envelopes, noise, CV and Gate. I also added CV and gate in. This required a switch as I'm using bananas and the original jacks use a switching jack to ground this connection when not in use.

I also just put in a completely new PSU and transformer.

I also replaced all of the fader caps with keys from a typewriter, which I actually think worked out great.








Still to do:

-Gate in isn't working properly.
-I ran out of yellow LEDs so haven't added indication for the Gate output
-Although a CV in is available on the back on a 1/4" jack, I like bananas so I need to add that to the front panel.

When I can be bothered I'll take a photo of the inside, there are a tonne of pcbs behind the panel as I ran everything through a buffer with gain to bring the levels up to full modular standards. It plays nice with modular! Smile Smile!
home_listening
More shots:

Outputs with transistor buffering for LED



Output buffering with level control. The trimpots are wired as voltage dividers which are then buffered a TL074 with x2 gain.


New PSU and transformer, just LM7815/7915. I wouldn't dream of fixing the original supply, it is 40 years old.


Glory shot. You can see how I used a 34pin IDC ribbon between the main PCBs and my outputs. This can be disconnected at both ends for maintenance. I kind of ran out of room for more bananas because of the PSU but could squeeze in a couple more maybe, at least one for filter CV in. I also want to add an audio in jack at some point. Easy to do.
scozbor
amaze! we're not worthy we're not worthy
home_listening
Thanks!
thetwlo
Beautiful work! ...and looks like a a lot of work to do it right.
basicbasic
To resurrect this thread:

Could anyone who has added CV-in to an SH-3a please take the time to explain the process to me? I found some instructions online but I was wondering if these could be confirmed and/or expanded upon.

Mine already has Gate in so CV would be the obvious next step.

Cheers,
Jamie
home_listening
The VCO jack on the back. I rewired mine to the banana jack on the front panel and added some offset/rescaling. I also think I had to change the input resistors a little. Should be R124/R125 before the buffer transistor.

I'm away for a year and have found homes for everything - otherwise I'd look it up. I also have all of my service notes back in Melbourne too. I hope this is a point in the right direction - wish I could be of more help. The SH-3a is a fucking amazing synth.
home_listening
Also; In case anyone has issues with the LM3216 chip dying it is worth having a few solutions written down, Ie searchable from google or whatever.

The chip is just 6 flip flops cascaded and tapped. I built two replacements, one using 3 CD4013 ICs and another using discreet transistor flip flops. Both worked great, the CMOS version sounded a little harsh to my ear, though I didn't use any PSU bypass caps.

I designed a PCB for the discreet replacement:

basicbasic
Thanks home_listening

It sounds a bit above my DIY skills right now. I was hoping there would be a 1v/oct point I could solder to but I probably should just get the Kenton socket kit.
home_listening
I can't remember the original range of the VCO CV in on the back, have you tried it with that yet? You may be able to scale the CV coming in before it hits the keyboard.

Can you provide details on how the Gate input was done? That was a real fuck around.
basicbasic
I just tried the VCO Cont. input on the back and it doesn't seem to respond to any obvious CV scale, as opposed to VCF cont which seems 1v/oct. In fact I can only get a response from the VCO if I invert the signal.

The gate input I had done years ago along with audio-in by a Sydney Tech firm - Phase Engineering, who I think were connected with Roland in some way.
basicbasic
I just opened it up and they have used a little circuit on a breadboard with a trimpot that seems to adjust the sensitivity of the trigger input.

I also found what seems like a point on the board that responds to pitch CV, though not at a perfect 1v/oct.

Anyway, somehow I ended up stuffing the trigger mod so i'll have to take it to a tech anyway - might as well get them to set up CV while it's on the bench!
boblav
Hi,
I acquired only the "semimodular" part of the Roland sh 3a, without the keyboard, only the "head". So, it sounds fine, but obviously I can t produce different tones (pitches). Could I use the VCO rear input in order to connect my 3U Doepfer A 190 MIDI CV/G module or Kenton USB Solo CV converter? If not, can anybody tell me the way I can connect or where wire It? Thank s
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