Korg DW8000, Mono/Poly, MS-20...

Hello:
I'm having dificulties in troubleshooting a tune problem on a MS20 synth.
When I press a key the note stays tuned correctly, but when the key is released, if I have VCA HOLD or RELEASE above 0, the note tunes to half tune down (If I press a C3 note, when released it assumes a B2 note).
I searched thru several posts but couldn't find anyone with a similar problem...
Freq mod knobs are set at zero.
Also:
- Jacks were reviewed and ok;
- Changed one of the VCA ICs which was dead but causing a diferent problem, not tune related;
- Changed transistor Q23, Capacitor C6 and IC5 just to check;

Q23 has 5VDC at is gate. When a key is pressed the Q23 gate's voltage drops to -1,5 VDC (wouldn't the normal be drops to zero?)
After release the key, Q23 gate gets again 5VDC.
Any help will be greatly appreciated.
Thanks!
Best regards
José
Portugal

Hello José

There is a group on yahoo which is specifically devoted to classic
(pre-MIDI) analog Korg synthesizers, it's called the KorgKornucopia.

http://launch.groups.yahoo.com/group/korgkornucopia/

I think if you ask your question in that group, you will get responses
from people much more familiar with the MS-20.

Regards,
David

On 08/27/2012 03:46 AM, letcista wrote:
> Hello:
> I'm having dificulties in troubleshooting a tune problem on a MS20 synth.
> When I press a key the note stays tuned correctly, but when the key is released, if I have VCA HOLD or RELEASE above 0, the note tunes to half tune down (If I press a C3 note, when released it assumes a B2 note).
> I searched thru several posts but couldn't find anyone with a similar problem...
> Freq mod knobs are set at zero.
> Also:
> - Jacks were reviewed and ok;
> - Changed one of the VCA ICs which was dead but causing a diferent problem, not tune related;
> - Changed transistor Q23, Capacitor C6 and IC5 just to check;
>
> Q23 has 5VDC at is gate. When a key is pressed the Q23 gate's voltage drops to -1,5 VDC (wouldn't the normal be drops to zero?)
> After release the key, Q23 gate gets again 5VDC.
> Any help will be greatly appreciated.
> Thanks!
> Best regards
> José
> Portugal
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>