The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Synths for sale  Search Gearslutz Go Advanced
MS-20 problems
Old 10th July 2012
  #1
Gear Maniac
 

MS-20 problems

I just received Korg MS-20 that I recently bought. I got this through eBay auction and the original auction said things like:"ALL BUTTONS KEYS FULLY WORKING." and "HAS BEEN CHECKED AND SERVICED BY OUR AUDIO SERVICE DEPARTMENT", except they aren't and I quess it wasn't (under the keybed there was a huge pile of "dust dogs" and rusty screws here and there).

Everything went smoothly with the courier service, the box was intact and the synth was properly packed. So I quess the shipping is not the thing to blame here.

The problems are:
1. Faulty Envelope Generator 2: Sustain is constantly on and Hold-knob does nothing.
2. Modulation Generator leaks to Frequency Modulation, causing constant modulation to oscillators.
3. Pulse Width-knob is not fully working. It stops modifying the signal at 3'o'clock

And here is a quick video I made to illustrate the problems:



Question is, should I send this back (they offered return 7 days after delivery) or should I find someone here in Finland to repair this or try to do it myself (if it's couple of broken IC, I can change them myself/with help of my friend who is a real soldering wizard)?

Thanks guys and gals!
Old 10th July 2012
  #2
AvS
Lives for gear
Thats a bummer man. :(

Your pulse Width-knob is working corretly though. The width of the pulse get so narrow that the waveform simply dissapears past 3'o'o clock - perfectly normal on an MS-20.

I have experienced the same problem with the lfo bleed on another synth. Was two dried out capacitors in the psu that was really easy to fix. Might not be the same issue here but perhaps it is.

Tough question if you should fix it with the help of your friend or send it back. It's proberbly an easy fix but they did rip you off and this kind of behaviour should have consequences. Maybe tell them whats wrong and ask them to cover the repair? Perhaps a long shot but If you send it back they will most likely just rip someone else off.
Old 11th July 2012
  #3
Lives for gear
 
Xero's Avatar
The faulty envelope is likely caused by a dead 4069 CMOS IC in the EG circuit. That same IC is used in a few places in the ms-20 and often dies. On mine, there's one that's part of the ESP circuit that died, causing my ESP not to function correctly.

4xxx series cmos IC's are often dead or dying, modern ones are made to much better standards, some would say, replace them all...but that might be overkill.

I'd probably look for any CMOS ic's as part of the other circuits that you're having issues with, more than likely that's the cause, or, perhaps your knobs just need cleaning.

If you do decide to keep it, at the very least, get a partial refund from the seller.
Old 11th July 2012
  #4
Gear Maniac
 

Ok, didn't know about the pulse width knob. Now that I do, it makes sense.

The seller was sorry and told that they allways check the gear prior to sending it out, but this time something else has happened. He also told me to get it fixed here in Finland and they will cover the costs, but I should get a quote first.

Things are starting to look better, now I just need to know where to get this repaired.
Old 11th July 2012
  #5
Gear Maniac
 

Quote:
Originally Posted by Xero View Post
4xxx series cmos IC's are often dead or dying, modern ones are made to much better standards, some would say, replace them all...but that might be overkill.
Yeah, there are 18 * 4XXX series IC's and 5 * 14XXX series IC's, pretty much every IC should be replaced then.

Quote:
Originally Posted by Xero View Post
I'd probably look for any CMOS ic's as part of the other circuits that you're having issues with, more than likely that's the cause, or, perhaps your knobs just need cleaning.
I was also thinking about spraying the knobs, but I didn't want to open the MS and I also think that the problem lies a bit deeper - like in the IC's or caps.

Now I just have to find a technician to fix mah baby.
Old 7th October 2012
  #6
Gear Nut
 
jasonM's Avatar
Quote:
Originally Posted by Bergman View Post
I just received Korg MS-20 that I recently bought. I got this through eBay auction and the original auction said things like:"ALL BUTTONS KEYS FULLY WORKING." and "HAS BEEN CHECKED AND SERVICED BY OUR AUDIO SERVICE DEPARTMENT", except they aren't and I quess it wasn't (under the keybed there was a huge pile of "dust dogs" and rusty screws here and there).

Everything went smoothly with the courier service, the box was intact and the synth was properly packed. So I quess the shipping is not the thing to blame here.

The problems are:
1. Faulty Envelope Generator 2: Sustain is constantly on and Hold-knob does nothing.
2. Modulation Generator leaks to Frequency Modulation, causing constant modulation to oscillators.
3. Pulse Width-knob is not fully working. It stops modifying the signal at 3'o'clock

And here is a quick video I made to illustrate the problems:



Question is, should I send this back (they offered return 7 days after delivery) or should I find someone here in Finland to repair this or try to do it myself (if it's couple of broken IC, I can change them myself/with help of my friend who is a real soldering wizard)?

Thanks guys and gals!

Hi Bergman, did you get to fix your ms20 or did you return it?
i also just bought one which fits your exact description ( Dirty) and it has the VERY SAME problems!..... whats even more worrying , the seller had the same words in the description : "VINTAGE SYNTH KORG MS20, USED IN PRO STUDIO FOR SEVERAL PROJECTS. ALL BUTTONS KEYS FULLY WORKING. EU POWER PLUG. HAS BEEN CHECKED AND SERVICED BY OUR AUDIO SERVICE DEPARTMENT" .

Was the seller from Holland by any chance?
anyway, it does come with a 3 months warranty and the seller excepts returns . so i might return it if fixing it is going to be an epic of a story.

Please let me know weather you returned it and i bought it
Old 7th October 2012
  #7
Lives for gear
 
NYMo's Avatar
 

Name and shame !
Old 7th October 2012
  #8
227861
Guest
There's another thread talking about how bad ebay sellers are. I have been scammed by many with many of my synths. Send it back get your money back. Keep detailed pics and vids of the problems in case they won't refund. File a claim with ebay.
Old 7th October 2012
  #9
Gear Nut
 
jasonM's Avatar
Quote:
Originally Posted by NYMo View Post
Name and shame !

I am hoping that it wont come to it and that it is just a coincidence ( though that voice in my head is telling otherwise) .

I contacted the seller to point out the faults .... i will wait to see what he has to say . i thought about returning it but i really don't want to risk " i have not received the item" and lose out twice. so a partial refund is what i want... i think

I might just get it fixed will update you.
Old 7th October 2012
  #10
Gear Nut
 
jasonM's Avatar
Quote:
Originally Posted by draven5 View Post
There's another thread talking about how bad ebay sellers are. I have been scammed by many with many of my synths. Send it back get your money back. Keep detailed pics and vids of the problems in case they won't refund. File a claim with ebay.
Thank you for the advice.
The only thing is , what if i return it , and he claims he never got it or that its not his signature on the "received" papers?. i understand that Ebay has the buyers protection etc as well as the seller accepting returns but... i dont want to endure a long winded process coupled with the risk of losing the machine it self .

Thanks again and i will post updates.
Old 7th October 2012
  #11
Gear Maniac
 

I never sent it back. I got it fixed by a pro here and it only took about 2 months (finding the pro, because there aren't many here in Finland, delivering the synth to him, waiting for the repairs and getting it back).

The problem was two broken potentiometers. The one that controls EG2 "hold time", causing the infinite hold and "frequency modulations" MG/T.EXT potentiometer that caused constant modulation to oscillators. Also the power cords was changed for IEC-plug (C14).

These repairs costed 90€ and was refunded back to me by the seller. And yes, he is from Holland.

Hope you get yours fixed, MS-20 is a bitchin' synth!
Old 9th October 2012
  #12
Gear Nut
 
jasonM's Avatar
Quote:
Originally Posted by Bergman View Post
I never sent it back. I got it fixed by a pro here and it only took about 2 months (finding the pro, because there aren't many here in Finland, delivering the synth to him, waiting for the repairs and getting it back).

The problem was two broken potentiometers. The one that controls EG2 "hold time", causing the infinite hold and "frequency modulations" MG/T.EXT potentiometer that caused constant modulation to oscillators. Also the power cords was changed for IEC-plug (C14).

These repairs costed 90€ and was refunded back to me by the seller. And yes, he is from Holland.

Hope you get yours fixed, MS-20 is a bitchin' synth!



Thank you so much for getting back to me. ok then , so its not the same ms 20 , though both have the exact same problems , and , same seller .

So far , he is still sticking to the company line of "all checked all serviced..." and has asked what do i want to do ... i want him to pay for the repairs , im just waiting for a quote . if he gives me any headache , i might even fly out there and ask for a replacement of a refund

Thanks once again
( and yes they are amazing )
Old 8th December 2012
  #13
Gear Nut
 
jasonM's Avatar
Update:
The e-bay seller has paid for the repairs cost. i found a brilliant repair team in Suffolk and got the MS20 Back in working order , they cleaned it and even changed the EU Power plug to a Uk plug .

Although the seller paid for repairs, i would never buy from him again because how he described the ms20 was misleading. Just amazed at how he has such good Ratings.

it's a shame.... he did have some amazing vintage s
Thanks again for all who helped out with advice.
Old 22nd May 2014
  #14
Lives for gear
 

I'm having problems with EG2 on an original MS20.

Its not sustaining all the time, its like there is no trigger off when letting go a key, so it continues through the ADSR cycle, except for no release at all. Not too sure what it could be.


Seen more than one place mentioning the 4069 CMOS IC, would that be likely to be causing the synth to think it's permanently triggered? Trying to use the ESP to trigger the sort of achieved the opposite.

Quickly looking at the schematic, could it be the TL081 causes problems?
Old 28th May 2014
  #15
Lives for gear
 

Apologies for the bump, but any ideas?
Old 4th September 2018
  #16
Here for the gear
 

Hi,

thanks to this thread I could fix my MS-20. I had a problem with infinite notes using EG2 so I could only use the synth with EG1 patched. I checked all the potentiometers of EG2 and they were displaying the right resistance values.

Closed to the EG2 pots there are three 14 pin IC, one 4069 (IC-23) and two 4007 (IC-19 and IC-22). I changed the three of them, testing after each one, but only the last one I soldered fixed the problem. It was IC-22, so 4007 in my case, but I recommend getting some replacement of both as I've read 4069 is often the faulty one as well.

I got the parts from Syntaur, and luckily they were not too expensive :

4007 : IC, 4007 dual FET/inverter
4069 : IC, 4069 hex inverter

hope this helps someone and thanks to the people posting here, I had a place where to start.
Old 3 weeks ago
  #17
imm
Here for the gear
 

hi, i thought i would resurect this thread rather than starting another ms20 troubleshooting thread...

i was just wondering what the reason could be that my LFO does not allow me to go to really slow rates. if i turn the rate all the way down or already at around 8 o' clock it will not return from its cycle and the LFO light stays on infinetly/until i speed it up again. i have also observed the lfo to be very inconsistent in it's rate and will drift quite a bit (no matter the speed), so i am assuming the lfo is getting pushed out of it's normal LFO range and needs some help to find it's way back.. i got this ms20 in pretty questionable state so i am hoping it is something having to do with the pot/mechanical parts? was just wondering if anyone else here has encountered such a problem before?
Old 3 weeks ago
  #18
Lives for gear
 

If the LFO is stopping at a certain point in the knob's travel and resumes when you turn it back, it's likely a bad pot.

If it's intermittent, and jiggling the knob restores it, it's either a bad or dirty pot.
Old 3 weeks ago
  #19
Lives for gear
 
Xero's Avatar
wow I barely even remember replying to this, but look at me there years ago, hahaha. I'm almost feeling rusty now.

I'd start with the pots as others said - just buy some good high quality contact cleaner, probably something to have around anyway if you don't already, start there.

if that doesn't work then you may want to go off the previous lead - start tracing the lfo circuit back to those pesky CMOS IC's again....
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
yarrick19 / So Much Gear, So Little Time
7
sonicdom / Geekslutz Forum
6
headz / Music Computers
0
museician01 / Music Computers
1
emeline-rec / Music Computers
6

Forum Jump
Forum Jump