You are here

Korg MS20 Kit Mods

Knowledgebase READ-ONLY collection of topics moved from other sub-forums to preserve them from auto-pruning. Only Moderators can start/reply or move topics into this archive.

Re: Korg MS20 Kit Mods

Postby Martin Walker » Mon May 23, 2016 8:01 pm

Well done Hugh - all useful mods, and a useful reminder to all that at least the two of us get out our soldering irons occasionally and brush up on Ohms Law inside analogue synths ;)


Martin
User avatar
Martin Walker
Moderator
Posts: 16043
Joined: Wed Jan 13, 2010 9:44 am
Location: Cornwall, UK

Re: Korg MS20 Kit Mods

Postby Zukan » Tue May 24, 2016 8:37 am

Well done Hugh! You can actually see those components? I can barely see the board. There's green there somewhere right?
User avatar
Zukan
Moderator
Posts: 8876
Joined: Fri Sep 12, 2003 12:00 am

Re: Korg MS20 Kit Mods

Postby Hugh Robjohns » Tue May 24, 2016 11:58 am

Zukan wrote:Well done Hugh! You can actually see those components? I can barely see the board. There's green there somewhere right?

;) I must admit the surgery to remove the 0 Ohm resistor did require the aid of reading glasses AND an angle-poise-mounted illuminated magnifier!

H
User avatar
Hugh Robjohns
Moderator
Posts: 27894
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Korg MS20 Kit Mods

Postby zenguitar » Tue May 24, 2016 12:41 pm

Hugh Robjohns wrote:
Zukan wrote:Well done Hugh! You can actually see those components? I can barely see the board. There's green there somewhere right?

;) I must admit the surgery to remove the 0 Ohm resistor did require the aid of reading glasses AND an angle-poise-mounted illuminated magnifier!

H

I am increasingly finding that I have to combine the angle-poise magnifier lamp and reading glasses these days. And that's just for the instructions/manual !!

Andy :beamup:
User avatar
zenguitar
Moderator
Posts: 10249
Joined: Thu Dec 05, 2002 1:00 am
Location: Devon
When you see a fork in the road, take it.
Yogi Berra

Re: Korg MS20 Kit Mods

Postby Martin Walker » Tue May 24, 2016 3:08 pm

I had to resort to a 1000-lux daylight lamp and something similar to this to manage the SMD mods on my Korg MS-20 Mini:

Image


Martin
User avatar
Martin Walker
Moderator
Posts: 16043
Joined: Wed Jan 13, 2010 9:44 am
Location: Cornwall, UK

Re: Korg MS20 Kit Mods

Postby Andy Cobley » Wed Aug 03, 2016 4:29 pm

Martin Walker's Korg MS-20 Retro Expansion:


http://www.yewtreemagic.co.uk/soundworlds3.php

Image

Very Nice !
User avatar
Andy Cobley
Regular
Posts: 102
Joined: Thu Sep 25, 2003 12:00 am
Location: Fife, Scotland

Re: Korg MS20 Kit Mods

Postby midierror » Thu Sep 15, 2016 10:00 am

Well... the PWM mod works.

But I've somehow lost the function of most of my keyboard trying the more elaborate FM mods!

The first 8 keys work, the rest do nothing..... via midi it works fine.

Can anyone help me out of my numerical mess?
User avatar
midierror
Regular
Posts: 261
Joined: Tue Apr 26, 2005 12:00 am

Re: Korg MS20 Kit Mods

Postby Martin Walker » Thu Sep 15, 2016 10:04 pm

Sorry to hear this midierror!

All I can say is that my mods use tried and tested tweaks, worked perfectly on my MS-20 Mini, and none of them cause radical changes to the original circuitry that could result in the things you're experiencing.

I can only think that you perhaps got a solder bridge in the wrong place when making the mods (SMD circuit components after all are extremely tiny, and I had to use a magnifying glass to see what I was doing).

It is however difficult to fault-find by remote control - let's hope someone else has an idea or two as to why only your bottom 8 keys still work, as that makes absolutely no sense to me.

Good luck!


Martin
User avatar
Martin Walker
Moderator
Posts: 16043
Joined: Wed Jan 13, 2010 9:44 am
Location: Cornwall, UK

Re: Korg MS20 Kit Mods

Postby midierror » Thu Sep 22, 2016 2:46 pm

yeah its quite strange really. I soldered with a magnifying glass and was exceptionally carefull.

I think it may have been a pull on the connecting cables from one board to the next. I wonder how the keyboard functions? I have no problems with midi in.

I am reluctant to dismantle the keyboard as I never went anywhere near it. Annoying as I have a gig next week!!
User avatar
midierror
Regular
Posts: 261
Joined: Tue Apr 26, 2005 12:00 am

Re: Korg MS20 Kit Mods

Postby BillB » Thu Sep 22, 2016 4:09 pm

Almost any instance of # keys work OK but # keys don't, is as a result of keyboard connectors coming loose, either over time or as a direct/indirect result of opening up a cabinet - especially if all is working via MIDI in. Or, as Martin says, just possible that something (solder/wire/screw) is shorting part of the keyboard detector circuit, again as a direct/indirect result of opening the case. No choice but to open up, look for any visual clues and reseat any connections.
:headbang:
BillB
Frequent Poster
Posts: 951
Joined: Mon Apr 07, 2003 12:00 am
Location: East Yorkshire

Re: Korg MS20 Kit Mods

Postby Hugh Robjohns » Thu Sep 22, 2016 4:30 pm

The keyboard is scanned by the microprocessor on the power and control board, and on the full-size version there are two connectors carrying the various connections to and from the keyboard.

The chances are you have partially dislodged one of those connectors, or that you have dropped solder or wire across the microprocessor terminals.

Shouldn't be too hard to find visually.

H
User avatar
Hugh Robjohns
Moderator
Posts: 27894
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Korg MS20 Kit Mods

Postby midierror » Fri Sep 23, 2016 2:04 pm

Thanks Hugh, I did de solder everything and go over it with a magnifying glass. its good to know how it functions, thanks for that...I will have a look again tonight.

I appreciate your help
User avatar
midierror
Regular
Posts: 261
Joined: Tue Apr 26, 2005 12:00 am

Re: Korg MS20 Kit Mods

Postby midierror » Tue Sep 27, 2016 2:01 pm

okay - I have some photos and an audio example of the state its in.

To save hijacking this thread - I'll start a new one here: http://www.soundonsound.com/forum/viewt ... 23&t=54536
User avatar
midierror
Regular
Posts: 261
Joined: Tue Apr 26, 2005 12:00 am

Re: Korg MS20 Kit Mods

Postby zaphod betamax » Thu Jan 26, 2017 8:50 pm

The fun really begins when you have 2 MS-20kits (modded or unmodded)
In my case they are both unmodded stock MS-20kits.

With Hz/V and Trig S you get
4 oscillators
4 EGs
and the ability to cross cable between the two and create some IMHO unique textures

As I run them both quite BPish, I fill in the bass with two Monotribes!
zaphod betamax
Posts: 3
Joined: Thu Sep 15, 2016 7:53 pm

Re: Korg MS20 Kit Mods

Postby Martin Walker » Fri Jan 27, 2017 9:06 pm

zaphod betamax wrote:The fun really begins when you have 2 MS-20kits (modded or unmodded)
In my case they are both unmodded stock MS-20kits.

With Hz/V and Trig S you get
4 oscillators
4 EGs
and the ability to cross cable between the two and create some IMHO unique textures

Audio demos please zaphod betamax! 8-) :thumbup:


Martin
User avatar
Martin Walker
Moderator
Posts: 16043
Joined: Wed Jan 13, 2010 9:44 am
Location: Cornwall, UK

PreviousNext