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CGS78 Envelope Generator- Problems with Decay and Sustain stages

CGS78 Envelope Generator- Problems with Decay and Sustain stages

2013-09-28 by piano392003

Wonder if anybody can help with this issue. I built the CGS78, using 1Megohm pots for the attack, decay and release controls. Using ±12V Power supply. Attack and release functions work fine. Sustain control has no effect on output level voltage (Output stays at about 10.6 volts with trigger present). Decay control has no effect whatsoever. Tried doubling C Capacitor from 1uF to 2uF with no change in performance.
Any suggestions?

Re: CGS78 Envelope Generator- Problems with Decay and Sustain stages

2013-09-28 by cg_synth

There is probably a construction error in the area of the sustain pot. perhaps the pot isn't wired to the correct pads. Perhaps you have a wrong transistor installed. C will have no effect on the sustain voltage.

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---In cgs_synth@yahoogroups.com, <cgs_synth@yahoogroups.com> wrote:

Wonder if anybody can help with this issue. I built the CGS78, using 1Megohm pots for the attack, decay and release controls. Using ±12V Power supply. Attack and release functions work fine. Sustain control has no effect on output level voltage (Output stays at about 10.6 volts with trigger present). Decay control has no effect whatsoever. Tried doubling C Capacitor from 1uF to 2uF with no change in performance.
Any suggestions?

Re: CGS78 Envelope Generator- Problems with Decay and Sustain stages

2016-01-21 by piano392003

I'm resurrecting this message in the hope that somebody can help me.
I ordered these PCBs from Ken Stone in 2013. It comes in a pair of two. I built one with parts that I sourced from mail order. I built the second one from parts that I sourced from Elby Designs, at least a year later. Both units have the same issue. Attack and Decay works fine, although the scope shows the times are rather quick. I can't get the Sustain step to happen. I am using a ±12Volt supply.

Does anyone have a clue?
Thanks,

Re: CGS78 Envelope Generator- Problems with Decay and Sustain stages

2016-01-21 by Ken Stone

No idea. Diodes in backwards? Transistors in backwards? Missing your main cap? Look for some sort of construction error that you would have repeated.
Ken
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On Thu, Jan 21, 2016 at 1:20 PM, piano392003@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I'm resurrecting this message in the hope that somebody can help me.
I ordered these PCBs from Ken Stone in 2013. It comes in a pair of two. I built one with parts that I sourced from mail order. I built the second one from parts that I sourced from Elby Designs, at least a year later. Both units have the same issue. Attack and Decay works fine, although the scope shows the times are rather quick. I can't get the Sustain step to happen. I am using a ±12Volt supply.

Does anyone have a clue?
Thanks,




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

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