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VC-ADSR/VCA with no time
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author VC-ADSR/VCA with no time
terjewinther
Moving on to the next error, I see that many others have issues with their ADSR build. I read through a lot, but none had my problem, so here I go:

I have an old VC-ADSR issue 2 board that I put together with a 4pot issue 1 board. It responds to gate input, and outputs a CV (both positive and nagative from the correct outputs) and lights the LED in accordance to the sustain pot setting. A CV into the sustain CV input (together with some setting on the sustain CV pot) varies the sustain level on the envelope. And sound into the VCA input is coming out properly. So there are a lot of things working.

However, there is (almost) no time components involved. No attack, decay or release time, no matter what the pot settings are. There is a tiny, tiny amount of time when all pots are set to max, and switching over to the longer time cap causes a microscopically longer time, but we are still in the extremely short time frame, with barely noticeable times (so it is really fast).

I did read up on the circuit description, which was a tough read, but I did grab most of it. Because of that I swapped out the CD4052 IC and the THAT2180LC IC, but still no change. I could try swapping out some of the TL072 ICs, but somehow I think I am missing the point. Any idea where to go next?
Synthbuilder
It may be a good idea to remove the four pot board temporarily and check that the ADSR board works as it should first. Remember to short out the correct pins on the AD and SR headers. If the ADSR still fails to work correctly then check that R27, R26 and R45 are the correct values. Check that pin 7 of U3 moves from 0V to 12V or so when the release pot is moved - 0V being the minimum release time.

Clearly if the ADSR works without the Four Pot board in place the problem then lies within either the wiring between the two boards or the four pot board itself. Since the sustain pot works my guess is that the Four Pot is working fine and problem is the ADSR board.

Tony
terjewinther
Yes, disconnecting the 4pot board returned the ADSR to correct working order. So clearly the error is with the 4pot board.
I double-checked the connections (as I have on occation crossed wires before), but they are correct.
The error is that voltage is sent from the ADSR board to the 4pot board, but not returned.
I checked the 4pot board for correct build, as there are many ways to build the board depending upon the use/connection, but all seems to be correct.
Strangely enough, the CV for sustain is working, while all the others donĀ“t.
It could be faulty TL072 op-amps, but it seems strange that they should all be faulty. Seems more like a general error, maybe with the power to the PCB itself. Need to debug, I guess.
terjewinther
Found the error. It was a poor connection. All working good now.
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