Anyone around to help me troubleshoot? (VRG/COTA FILTER)

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chemical_oli
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Anyone around to help me troubleshoot? (VRG/COTA FILTER)

Post by chemical_oli » Thu Aug 30, 2018 9:28 am

Hi this is my first post to the Oakley forums so I would like to thank you all for the thorough and valuable information contained therein, It absolutely inspired me to get into 5u Modular and begin constructing an Oakley system, not to mention the rigorous and helpful documentation Tony has put together for his modules, all of which have been an immense help to me setting out.

I am going about the process of building my first 5U modular from scratch which at present includes an Oakley 1of3 Osc, COTA Filter, Dual LFO and a Variable Ramp Generator, all powered by an Oakley PSU and Dizzy distribution board, juiced with a Yamaha PA-30 Line Lump.

The control voltages and gates are being converted from the Midi out of an Octatrack MK1 by Pete Kvitech's MIDI2CV board (which I believe is a clone of a mutable instruments board, and is the only non Oakley module present in the system at present)

I am having trouble with the VRG and COTA filter. Both read happy voltages (15V between the relevant polarity and ground and the connector) There are no components heating up and I have tested each IC is rested properly in its socket.

The VRG gate input will not register any input (although continuity between the jack and pin 2 of the UPR Header is solid). The Slew is registering as a green flash and is tracking properly with changes in the up and down controls to function (very nicely) as a rudimentary EG. I get no interaction from the three way selection switch, and although I somtimes see a flash of red from the LED when powering on, that is the only time I have seen it change colour.

The only substitution I made was swapping the AD712 for a TL072CN.

A concern I have is that I have somehow misread the documentation and wired the LED the wrong way, I have it attached is the flat (short legged) side of the LED connected to the corresponding square hole on the PCB.

The LED used in the project can be found at this mouser page.


As for the COTA filter, I am not getting any resonance unless I put a jack into the feedback control input loosely 3/4 of the way in. The rest of the appears to work and sound fantastic!

I hope I have not doomed the project by using cheapo connectors! (I have used Plastic Stereo Rean sockets, the mouser page for which can be found here.

Any input would be greatly appreciated! I dont mean to ask any of you to do my homework for me, but I have been chewing this one over for days now and with how good it sounds when it dosen't work, I cant imagine how good it will sound when it does!

Thanks
chemical_oli

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Synthbuilder
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Post by Synthbuilder » Thu Aug 30, 2018 10:04 am

Both those problems could be due to incorrect wiring of the sockets. The VRG uses the normalising lug of the SLEW IN socket. Check the wiring on that socket first. Then try inputting a gate signal into the slew input and see what happens. You should get a traditional attack-release signal from the output and the LED should light up when the output is above zero volts.

The COTA also sounds like a miswiring - this time of the FEEDBACK socket. If the normalising lug isn't making connection on that socket then the resonance won't work. I wonder whether you've got the ground lugs and signal lugs swapped.

Sorry if you know this already, but those Rean jacks are three pole TRS (tip-ring-sleeve) sockets with normalising lugs on all three poles giving them six lugs in total. The ring lugs (the two middle ones) are not to be used as these are only for TRS or stereo jack plugs. Modular patch leads are mono so only use the tip and sleeve connections. Thus you should only be using the tip lug, the tip's NC lug and the sleeve lug (for panel ground).

Tony

chemical_oli
Learning to Wiggle
Posts: 4
Joined: Sun Nov 12, 2017 5:27 pm
Location: UK

Post by chemical_oli » Thu Aug 30, 2018 3:17 pm

Thanks so much for the quick reply!

I had wired it incorrectly! It is working great now :guinness: :guinness: :guinness:

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