Hi, I just debugged a DUSG yesterday that had this very problem. Check
your transistors, specifically the NPN's in the current source. I had used
2n3906's in combination with 2n5089's and I got this very behavior. I
believe either it was the combination or, much more likely, the transistors
were installed backwards - looking at the datasheet for 2n5089's it looks
as though the silkscreen package outline on the PCB is in the opposite
orientation. I don't think I ever checked these before installing.
Anyway, I swapped them out with 3904's oriented the correct way. These
are (ordinarily) the same as the pinout for 5089's, and opposite the
silkscreen on the PCB.
One thing I noticed is that I still got the rise time to modulate, but the
knob had to be full CW and I needed some significant CV in.
your transistors, specifically the NPN's in the current source. I had used
2n3906's in combination with 2n5089's and I got this very behavior. I
believe either it was the combination or, much more likely, the transistors
were installed backwards - looking at the datasheet for 2n5089's it looks
as though the silkscreen package outline on the PCB is in the opposite
orientation. I don't think I ever checked these before installing.
Anyway, I swapped them out with 3904's oriented the correct way. These
are (ordinarily) the same as the pinout for 5089's, and opposite the
silkscreen on the PCB.
One thing I noticed is that I still got the rise time to modulate, but the
knob had to be full CW and I needed some significant CV in.
On Sun, Feb 17, 2013 at 9:55 AM, adematteo <adematteo@...> wrote:
> **
>
>
> Hi guys, I am noticing that the rise time on my dusg's doesn't seem to
> have very much effect in a typical way.
>
> I know this circuit is not a typical envelope generator so i'm curious if
> it's just the way this circuit works, but if i feed a trigger in and have
> the rise time set to full cw position it still fires exactly when it gets
> the trigger but it does take the sharp edge off.What i would expect is that
> i would get a slow rising voltage ?
>
> Like i said just trying to figure out if i should expect this behavior or
> if i did something wrong when building it.
>
> Thanks, Tony
>
>
>
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