[sdiy] Moog 911A dual Trigger Delay

[Ullrich Peter]

Hi!

According to this schematics R12 should be 2k7 and not 27k (and so the Q5 swithcing range is limited):

http://moogarchives.com/911as.jpg

Remark: Your original Moog schematics can not be loaded:
ftp://ftp.xmission.com/pub/users/d/dingebre/outgoing/Moog911A1.1.pdf

Ciao
Peter

http://www.ullrich.at.tt



-----Ursprüngliche Nachricht-----
Von: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] Im Auftrag von David Ingebretsen
Gesendet: Freitag, 26. April 2013 05:54
An: synth-diy at dropmix.xs4all.nl
Betreff: [sdiy] Moog 911A dual Trigger Delay

Hi everyone! Long time lurking :)

I would like to beg for some ideas, please. I am trying my hand at a Moog 911A Dual Trigger delay. The original Moog schematic, the data sheet for an
E203 FET, and my schematic capture are at:

ftp://ftp.xmission.com/pub/users/d/dingebre/outgoing/E203.pdf
ftp://ftp.xmission.com/pub/users/d/dingebre/outgoing/TriggerDelay.pdf
ftp://ftp.xmission.com/pub/users/d/dingebre/outgoing/Moog911A1.1.pdf

I'm pretty sure I have the circuit properly entered into Eagle, and I'm think this Moog schematic should work as it is shown.

The initial stage up to the FET, Q3, works fine. The problem is Q6 never turns off, so something is happening between the FET and Q6.

I removed the FET in case it wasn't turning off, which means (assuming I understand the circuit, which is a reach) means Q4 is off, Q5 is on, Q6 is off and the output floats, like a good S-Trigger should. However, even removing the FET, which I think should make sure there is no trigger output,
Q6 is still on. I'm assuming the transistors are operating as switches given this module is dealing with triggers and not audio signals.

If I short Q6 base to ground, it turns off and the trigger is off.

Does anyone have a suggestion on how to trouble shoot this thing? I'd like to think I can make something this simple work, but maybe that's too much to expect :)

I'm enclosing the FET data in the hopes someone can help me find a substitute. I'm trying a NTE466 which the NTE site recommended, but I'm open for ideas.

Thanks everyone.

For fun, here is the latest info on my Synthasystem:
http://analoguerealities.blogspot.com/

David

David M. Ingebresten
dingebre at 3dphysics.net
dingebre at CFandE.com


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