Frequency Central System X ENV build/debug question

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wjmwpg
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Frequency Central System X ENV build/debug question

Post by wjmwpg » Wed Oct 09, 2019 1:58 pm

I recently purchased a bunch of Frequency Central boards (DUAL XVCA, State 700 VCF and two System X ENVs). The XVCA and State 700 VCF builds went fine and work perfectly. 

Unfortunately both of the System X Envelopes have a Sustain value of 100% no matter where the sus pot is positioned. The attack and release work as they should, and the decay can't be judged as functioning or not with the sustain always at 100%.

I received Ver. 2B panels for the envelopes and proceeded with the build document Version 2 / March 2013. (http://www.frequencycentral.co.uk/wp-co ... ld-Doc.pdf)

The only area where I strayed from the parts as labelled on the PBCs was replacing the LF351's with TL071's as Rick mentioned that "duff" LF351's were making the rounds. I also did this on the State 700 VCF build and that substitution went fine. 

I've messaged Rick about the issue, and requested a schematic or suggestions to help track down the problem, but without response. 

As this is my first ENV build I'm not familiar enough with the circuit to pursue the issue without a schematic (or at least some helpful hints where to look). If anyone here has any ideas I'm all ears and appreciative.  :help:

Cheers,
James

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sir stony
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Post by sir stony » Wed Oct 09, 2019 2:44 pm

This question should rather go into the tech/DIY sub...

I'd guess you made a mistake somewhere, as both ENVs behave the same. When I made two for my monobloc 01, which was my first eurorack "module", I had no problem at all with these. I had another problem with the vco tuning, and when I mailed Rick about that, he replied really quick and pointed me to the solution right away, super helpful! If he hasn't answered to you yet, there will be a reason. Maybe he's off to somewhere else?

If you provided a photo of your build, that might help, too. ;)

miminashi
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Post by miminashi » Wed Oct 09, 2019 3:02 pm

FWIW, I've assembled 6 of these envelopes and they've all worked great for me. I don't know anything about the circuit so I can't help you debug. I would email Rick if you haven't already, he's always been very helpful with me.

P.S. I used a smaller value (I think 4.7uF instead of 10uF) for the SLOW cap to bring back a little snap, otherwise the attack is a smidge soft for my tastes.

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wjmwpg
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Post by wjmwpg » Fri Oct 11, 2019 7:54 pm

Yup, I dropped some 560 ohm resistors where 560K ohms should have been. My bad. Luckily a helpful AH member spotted it in a photo of my build. These ENVs sound great.

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fragletrollet
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Post by fragletrollet » Sat Oct 12, 2019 12:55 am

I had the same problem building mine. Turned out to be a bad batch of ics from tayda (lf351)

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