Discussion about the Korg PolySix synthesizer

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@bellsouth.net> wrote:

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> 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?
> 
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