Korg Forums Forum Index Korg Forums
A forum for Korg product users and musicians around the world.
Moderated Independently.
Owned by Irish Acts Recording Studio & hosted by KORG USA
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

MS20 Kit mod/test points non functional
Goto page 1, 2, 3  Next
 
Post new topic   Reply to topic    Korg Forums Forum Index -> KORG MS20
View previous topic :: View next topic  
Author Message
futureimage



Joined: 02 Jun 2007
Posts: 16
Location: South Gloucestershire, England

PostPosted: Fri Apr 25, 2014 11:32 am    Post subject: MS20 Kit mod/test points non functional Reply with quote

Hi there,

So I've been modifying my MS20 (Kit) with some of the test points on the back of the voice PCB, as well as a few of my own. However, I've run into problems getting a lot of the VCO mods working. Here are my findings:

Osc 1 - all waveform outs pass directly through rotary switch. Therefore, wiring up individual waveform outputs was easy.
Osc 1 PWM - Modification works as expected (and sounds great may I add)

Osc 2 - Waveforms seem to pass through an analogue switch controlled by logic levels at the rotary. Individual waveform outputs are not accessible from the back of the voice PCB.

Here's where things get interesting/annoying:
Osc 1 and 2 outputs designated on the PCBs - no output.

Osc Sync - Input does not seem to work. Hardwiring the VCO1 sync out to the VCO2 sync in does absolutely nothing.

Osc 1 and 2 modulation inputs - Do not do anything whatsoever.

So what's going on Korg? Is there a cheat mode (akin to the key combination for switching filters) that we must enter to activate the test points? Did the designers unhook the above test points on the final run of PCBs?

Please note that I'm a competent synth builder and designer - I'm not a n00b with this stuff!

Cheers!
Fin Shakespeare
_________________
Unique designs and ideas in sound since 2005:
www.futuresoundsystems.co.uk
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
LivePsy
Senior Member


Joined: 23 Nov 2007
Posts: 347

PostPosted: Sun Apr 27, 2014 12:01 am    Post subject: Reply with quote

Thanks for the research because I would have ended up doing exactly your work.

B
Back to top
View user's profile Send private message
mmarsh



Joined: 04 Jul 2014
Posts: 11

PostPosted: Sun Jul 20, 2014 12:27 am    Post subject: Reply with quote

I found exactly the same thing. Is there any word from Korg?
Back to top
View user's profile Send private message
adammiller



Joined: 08 Aug 2014
Posts: 1
Location: Portland, Oregon USA

PostPosted: Fri Aug 08, 2014 5:52 pm    Post subject: Reply with quote

It's a shame, seeing how it's so clearly labeled. I don't really have anything to offer, but hopefully posting replies will get some attention. Any news?
Back to top
View user's profile Send private message
mmarsh



Joined: 04 Jul 2014
Posts: 11

PostPosted: Fri Aug 08, 2014 6:01 pm    Post subject: Reply with quote

I don't believe Korg participates here. I've never seen a reply from them on this issue.
Back to top
View user's profile Send private message
soundsafoolmusic



Joined: 31 Oct 2014
Posts: 1

PostPosted: Fri Oct 31, 2014 4:56 pm    Post subject: Reply with quote

Re Sync:

Looking at Auxrens findings on the MS20 mini, he added a diode to a switch and then soldered to the ms20 diodes.

Maybe all that is required for the kit version to work with the two solder points:

a couple of wires
a diode
a switch

http://www.auxren.com/2013/09/ms-20-mini-pcb-photos-and-osc-sync-mod.html

Would like to know if that works before I open up my kit and do it myself!

I can then add pwm and VCO1 separate outs at the same time. Very Happy
Back to top
View user's profile Send private message
mmarsh



Joined: 04 Jul 2014
Posts: 11

PostPosted: Fri Oct 31, 2014 5:00 pm    Post subject: Reply with quote

No, that does not work Sad
Back to top
View user's profile Send private message
easy_lee



Joined: 24 Jan 2015
Posts: 5

PostPosted: Fri Jan 30, 2015 1:46 pm    Post subject: Reply with quote

Is there any new information regarding MS-20 Kit modifications?

I've seen a posting on an auction platform for an MS-20 Kit with a sync mod. It seems therefore such a mod is possible.

Is there any official information from Korg about those patch points on the MS-20 Kit's PCB? I wrote to their tech support in Germany about it but got no reply.

I think it'a a bit weird that there are all those clearly labelled soldering points on the PCB yet there is no information about how to use them.

To the OP: How exactly did you implement the PWM mod? Did you add an additional CV input for PWM?
Back to top
View user's profile Send private message
LivePsy
Senior Member


Joined: 23 Nov 2007
Posts: 347

PostPosted: Sat Jan 31, 2015 1:31 am    Post subject: Reply with quote

The MS20M Kit desktop might have sparked an interest in modding our Kits, since we don't have the greatest MS20 anymore Sad
Back to top
View user's profile Send private message
Mr White



Joined: 04 May 2015
Posts: 9

PostPosted: Mon May 04, 2015 11:50 am    Post subject: Reply with quote

any news about mods and patch points?

I'm attempting wiring of vco1 waveform outs, pwm and sync.
Back to top
View user's profile Send private message
Jamie Munro
Full Member


Joined: 27 Sep 2013
Posts: 113
Location: England

PostPosted: Mon May 11, 2015 5:14 pm    Post subject: Reply with quote

Any success mr white?
_________________
Live fast, ride fast
Back to top
View user's profile Send private message
Mr White



Joined: 04 May 2015
Posts: 9

PostPosted: Tue May 12, 2015 9:06 am    Post subject: Reply with quote

successfully installed pwm, had a look at the sync mod from auxren and remork, one installed on the mini, other on vintage.
I think we have to figure the pcb because the kit reissue is completely similar with the vintage Smile

I added a pic of the VCOs of my Kit, you could see the transistor cluster right below vco1 pw and vco2 fine pitch pots.

from what I saw looking at vintage schematics, the trick with diode and switch is between Q2 and Q4

do not attempted yet because I'm not sure if I spotted Q2 collector and Q4 base correctly...

I tested that:

D4 sits between Q2 and Q3
D17 sits between Q17 and Q4

so I think that we should put the switch between Q2 pin facing down (collector?) and Q4 pin facing left (base?), any thoughts?

because, looking at the nod done on the mini it seems that the guy inserted the switch between the diodes, that in the kit were not the right connection...

here is the resource:
http://remork.blogspot.it/2011/11/korg-ms-20-modsschematics.html
http://www.auxren.com/2013/09/ms-20-mini-pcb-photos-and-osc-sync-mod.html


Back to top
View user's profile Send private message
Mr White



Joined: 04 May 2015
Posts: 9

PostPosted: Thu May 14, 2015 1:08 pm    Post subject: Reply with quote

there is something that still make me think..

diode.

in auxren mod, looking at where he soldered wires on diodes, he picked at the same polarity, as shown in the remork's vintage schematic.

with it in mind it seems that everything is reversed from what I fugured, so instead of Q2 and Q4 we shoud use Q3 and Q17?
Back to top
View user's profile Send private message
sjonp



Joined: 20 Oct 2011
Posts: 19
Location: San Mateo, CA

PostPosted: Wed May 27, 2015 9:36 pm    Post subject: Reply with quote

Mr. White,

I appreciate your research. As an owner of an MS-20 kit, I am planning to open my synth up to add PWM and osc sync. I am very interested in how this thread develops as I would like to have a clear path to performing the osc sync mod before I pick up my soldering iron.

Also, having some MS-20M kit, envy, I am wondering if there is a way to add FM to the MS-20 kit?

Thank you,

Sjon
Back to top
View user's profile Send private message
Mr White



Joined: 04 May 2015
Posts: 9

PostPosted: Fri May 29, 2015 4:56 pm    Post subject: Reply with quote

as no one takes the bill, I did Smile

followed my clue tu look the schematics of the vintage korg and not the KIT board.

trick is between Q3 and Q17 Wink





it sounds simply awesome...
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Korg Forums Forum Index -> KORG MS20 All times are GMT
Goto page 1, 2, 3  Next
Page 1 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group