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Freq Central System X Envelope peculiar Decay issue
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Freq Central System X Envelope peculiar Decay issue
smcumber
I recently built a Frequency Central System X Envelope as my first completed DIY module, and it seems to be fully functioning except for one issue - the decay does not behave normally.

The outputs/input, LED, switch, and attack/sustain/release are all functioning normally as far as I can tell. The decay seems to act similar to the sustain, adding DC voltage when a gate signal is provided.

What's also odd is that say I hold a note, if you turn the decay knob COUNTERCLOCKWISE (i.e. reverse from normal) the decay adds more voltage; in essence the "bottom" of the range of the pot is what you would expect the "top" to be, and also when you turn it to the left it drastically increases the voltage in a very small turn range in what sounds like almost steps.

I have scoured the PCB for poor solder connections or unwanted solder bridges but can't seem to find any. I was also pretty fastidious about using the correct value resistors and I double-checked the values on the few capacitors that were in the build.

Does anyone have any suggestions as to finding the root of the problem? The only thing I could think of it might relate to is that I "adapted" vertical 9mm pots to be right angle - meaning, I bent the vertical leads from the pots to be 90 degrees relative to the shaft, then snipped the fat parts of the leads so that they would fit in the smaller holes.

Here is the link to the build doc from Freq Central:

http://www.frequencycentral.co.uk/wp-content/uploads/2013/06/System-X- Envelope-Ver2-Build-Doc.pdf

The Decay pot I used is definitely A1M, the correct value. Any help is greatly appreciated.
Starspawn
A friend had two with similarish problems.
One was cured by changing the single opamp to TL071, other is still to get a more thorough examination of the actual board as parts have been changed etc.
smcumber
Hmm. It wouldn't be expensive to order a TL071 with my next Tayda order, but would like to figure out if that's really it cause I was planning on building two more if this works out. I might email Rick Holt directly about it.
oootini
think i've noticed similar on my build.

report back here if you get an answer please.

i put it down to a quirk of the original circuit because everything else seemed to work just fine.
smcumber
I'm glad I'm not just going crazy. I emailed Rick from Freq Central about it, hopefully will hear back.
4floorsofwhores
Same issue with mine. Only finished building last week and assumed i'd done something wrong
smcumber
Bummer. It seems like it might be something inherent with the PCB, I'm not sure if this is a new iteration of the design or something. I'm still waiting on a reply from him.
n0rd
I've built a couple of these and they work fine / as expected. Don't have this behavior.

The PCB's I have are green with "Ver.2B May 2013".

Steve
degeneratedsines
Is this still an issue? I was about to order a couple of those adsr

EDIT: oh well... just ordered two smile
degeneratedsines
Mine are working fine. cool
I used TL071 and 2N3906 PNPs because I had spare ones.
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