Discussion about the Korg PolySix synthesizer

No charge, other than parts and return postage, as long as you don’t mind me
posting the results to the group here. It’s an education thing, to enlighten
the group on things that can go wrong with a clone board build. We’re here
to help, right? It might take a couple of weeks to get it diagnosed and
going again, since I don’t have a lot of spare time. I can’t imagine it
would need much in the way of parts.

Don B.

 

  _____  

From: PolySix@yahoogroups.com [mailto:PolySix@yahoogroups.com] On Behalf Of
Mike
Sent: Saturday, September 17, 2011 11:10 PM
To: PolySix@yahoogroups.com
Subject: [PolySix] Re: Another KLM367 clone issue: MG Delay

 

  

Also,

How long do you think it will take to fix?

-Mike

--- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , "Mike"
<mborish_2000@...> wrote:
>
> I know you don't have the board, but do you have an idea of how much it
will cost? Also, how do you want to get paid?
> 
> -Mike
> 
> --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , Andrew
Jury <andy@> wrote:
> >
> > Strange! The only two real big differences between the 2SC945 and 2N3904
are
> > the leg positions and the Hfe. The 2N has a far superior gain in this
> > respect. Perhaps the difference in the current characteristics is
effecting
> > the timing constants in the circuit? I think I¹ll go and try a BC547 and
see
> > what happens...
> > 
> > Cheers,
> > Andy
> > 
> > On 28/07/2011 03:17, "backshall1 (dsl)" <backshall1@> wrote:
> > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > Okay, that didn't work. I unsoldered the positive side of C33 and
connected
> > > it to the other end of R98 and that made the problem worse. So, I put
the
> > > capacitor back, and tried a cross-legged 2SC945 like Malte said.
Problem
> > > solved. There sure seems to be a mismatch with the 2n3904 in this
circuit.
> > > 
> > > Don B.
> > > 
> > > _____ 
> > > 
> > > From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com>
> > > [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com> ] On Behalf
> > > Of
> > > backshall1 (dsl)
> > > Sent: Wednesday, July 27, 2011 6:22 PM
> > > To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com>
> > > Subject: RE: [PolySix] Another KLM367 clone issue: MG Delay
> > > 
> > > Yes, I sure have seen this. With a 2 second delay set, if I don't
press any
> > > keys for a while and then press one, the MG is on immediately. If I
play
> > > notes no more than a couple seconds apart, the delay is 2 seconds. Has
> > > anyone noticed that C33 is not connected as it appears in the
schematics?
> > > The schematics show it connected to the top of R98 and IC 14 pin 3,
but it
> > > looks like on both the new and old boards it is connected to the
bottom of
> > > R98 and the collector of Q5. Weird. Wonder if moving this would change
the
> > > problem?
> > > 
> > > Don B.
> > > 
> > > _____ 
> > > 
> > > From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com>
> > > <mailto:PolySix%40yahoogroups.com>
> > > [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com>
> > > <mailto:PolySix%40yahoogroups.com> ] On
> > > Behalf Of
> > > Malte Rogacki
> > > Sent: Wednesday, July 27, 2011 2:16 PM
> > > To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
<mailto:PolySix%40yahoogroups.com>
> > > <mailto:PolySix%40yahoogroups.com>
> > > Subject: [PolySix] Another KLM367 clone issue: MG Delay
> > > 
> > > This has come up in various degrees with several boards so I guess
this
> > > could be a more common problem.
> > > 
> > > Short description: MG Delay doesn't always work reliable
> > > 
> > > Long description: I'm getting different times for the MG Delay
depending on
> > > the time between key presses. If there is a longer time between key
release
> > > and new key press (several seconds) the MG Delay time will be
significantly
> > > shorter.
> > > It should be noted that this is also present with original KLM367
boards
> > > albeit to a lesser degree. For example, one original board I have has
a
> > > "regular" maximum delay of about 9 seconds; this drops to about 7
seconds
> > > under the above scenario.
> > > However with the clone boards the behaviour can be more severe. I'm
having
> > > one that behaves about the same as the original board; however another
one
> > > has a maximum delay time of about 7 seconds which drops to less than
one
> > > second in the above scenario.
> > > 
> > > I suspect T5 (Q5) to be the culprit here; swapping this with another
one
> > > resulted in a maximum time of about 7 seconds and a minimum time of
about 3
> > > seconds. However swapping this with the original 2SC945 (of course I
took
> > > care of the correct orientation) resulted in near perfect behaviour.
> > > 
> > > So the question is if the 2N3904 is really a good substitute for the
> > > 2SC945? There are of course some tolerances; however that those
tolerances
> > > result in such different results strikes me as odd. Or is that batch
of
> > > 2N3904 really that bad? What have the other clone builders
experienced?
> > > 
> > > [Non-text portions of this message have been removed]
> > > 
> > > [Non-text portions of this message have been removed]
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > 
> > [Non-text portions of this message have been removed]
> >
>





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