[sdiy] Re: A new Korg ms20 (or ms10...) riddle for you: ADSR retriggering
antoniotuzzi at gmail.com
Sat Mar 15 17:36:02 CET 2008
for the archives...
that was easier than expected...
the lm7915 was giving -25volts...
with all the consequences (retriggering and portamento bad behaviour...)
On Fri, Mar 7, 2008 at 10:25 AM, Antonio Tuzzi <antoniotuzzi at gmail.com> wrote:
> Hi friends.
> I have a KORG ms20 from a friend suffering for a strange EG2 behavior.
> the EG2 is an HADSR envelope generator, where the HOLD parameter
> simulate a sustained key
> the HOLD is working...
> the ATTACK seems to respect timing and so the RELEASE
> when the key is released, the RELEASE is working
> the problem is the SUSTAIN: when the level is lower than 3 the EG2
> automatically retrigger (that is not a bad at all: similar to the
> retrigger of the trapezoid in the EMS Synthis, but should be
> controlled by a switch at least...) and redo the ATTACK and DECAY
> phases, so the sound never reach the SUSTAIN level but is doing
> ADADADADAD and so on...
> If the SUSTAIN value is bigger than 3 the behavior is more erratical
> seems a comparator problem...
> examining the schematics for the EG2
> the IC20 (a 4558) pin 3 is the comparator involved, but I can't the
> see the connection to the retrigger that should come out from
> IC23 (4069) pin 10 (top right): the only connection is coming from
> IC21 (tl081) pin 6
> but ic21 seems to work as the A and D and R are working...
> I'll change as number one the IC20 and after the IC23..
> what is your guess ?
> thank you
> better visibility here (ms10 eg is the same!) but with ic numberdifferent
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