Random Number Generator Problem

[Jamforthelamb]

Hi Everyone,
I recently built an RNG, and it works pretty much as described except for one thing.
If you listen to Mr. Deeper's sound sample:http://www.midfielectronics.com/rng.mp3 you can hear in the sample that when a note is played it rings for a bit making all the little random noises. My build does that for about a half a second, and the mutes the note completely. I have socketed all the trannies, tried mutiple combinations of 2n222s, 2n3904s, and 2n4401's with little change regarding this problem.

My question is, is there anything I can adjust (maybe a resistor or cap) to help the signal sustain like the sample does? It almost seems like something in here isn't letting enough of the signal through, so it's gating itself.

Thanks,
JFTL

[Jamforthelamb]

This is the schematic for it. I used Tcobretti's layout to build it.

[tcobretti]

You should measure the voltages on all the transistors and post them here.

[Skreddy]

On first glance, I'd say that the 470k on the collector of Q2 is your most likely culprit for the gating problem.  Maybe sub in a 500k pot there?

[Jamforthelamb]

Tco: I'll do that asap.


Skreddy: I will definitely try that.

Thanks!
JFTL

[mattpocket]

I'm building this one as soon as the parts arrive so I will be following this closely, let me know how it goes and what you find...

Matt

[doug deeper]

there should be a good amount of sustain.
as long as you use the pn2222 for Q2....others may work as well.

[Jamforthelamb]

Matt: I'll keep this thread posted with what I find for ya.

Doug: OK, cool. I've been using all 2222's on my build because it keeps it from constantly oscillating. I just keep running into this sustain problem. I'm going to try and get the voltages of everything up here when I get home tonight.

Thanks,
JFTL

[mattpocket]

do a search for "weird pedals" a topic in my name, there were a load of guys who posted a lot of info about this build...might help you understand the circuit a bit better...

Matt

[Jamforthelamb]

Matt: That's the thread that made me want to build one in the first place

[tcobretti]

Constant oscillation is not a problem I had with mine, and I believe I tried some pretty high gain transistors (probly 2N5089s).  The oscillation could be caused by wiring, however, while the gating could be another problem altogether.  I would definitely check the vero strips very, very closely for solder bridges.

[Jamforthelamb]

Ok, here's the numbers:

Q1
C:1.8
B: .56
E: 0.0

Q2
C: .26
B: .50
E: 0.0

Q3
C: .50
B: .31
E: 0.0

Q4
C: .45
B: .51
E: 0.0

[tcobretti]

Ok.  I don't have mine anymore (it was built as a gift), but those values look very wrong to me.  I would check the top strip of the vero to make sure there are no solder bridges, and I would be sure you made all the cuts in the traces.  Q2 and Q4 look especially suspect, so I would also take a close look at the 100k resistor running to the bottom strip in the middle of the layout that connects the two transistors.