Discussion about the Korg PolySix synthesizer

Also,

How long do you think it will take to fix?

-Mike

--- In PolySix@yahoogroups.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, 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@yahoogroups.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>
> > > 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@yahoogroups.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>
> > > 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]
> >
>