log: building Oakley modules in dotcom format

[kdjupdal]

Intermezzo:
I exchanged the jack sockets on my dotKom SVF filter, from the open jacks to new switchcraft enclosed jacks. Much better! That took some time, though: I'm sure the module was assembled in less time than I spent exchanging jacks. But it's a good filter and it still works after 13 years. Now I just have to do it on the rest of my modules with open type jacks. I've noticed that the number of jacks in a modular system quickly adds up.

Open jacks: Here you can buy them with nut and washing machine(!)
Some bad machine translating there.

[kdjupdal]

Here are the VCAs finished: 4 modules, one built by Lower West Side Studios, but I've exchanged panel on that one so they all look the same. I've modified the panel graphics slightly. "Out A" is merely OUT and "out B" is DIFF. I was always wondering if you should use A or B (that is, untill I read the manual). Now I get the hint that DIFF is a difference signal.

PCB-side. Can you spot the one built by LWSS?

[kdjupdal]

I've also finished the VC-ADSR! Looks really nice (I think). The design layout is of course inspired by the Moon VC-ADSR, which I find very intuitive. And I went crazy and used a blue led. Will probably change to red after a while.

Wiring on this module took some time:

[kdjupdal]

VCA-X:
Quad channel vca and mixer. This is a really useful module.

Wiring was a nightmare - I spent two days wiring. But note, I built the module in an unconventional way - wiring every pot, switch and jack, because of my panel design. (And I did a mistake with the switches so I need to do them again.)

I've testet and calibrated the module. Seems to be one thing not working properly - channel one doesn't go to the MIX output.

[kdjupdal]

I have one problem with one of my Classic VCAs:

I was calibrating it and noticed that I can't get rid of the offset from the output (calibration no. 1). I only get it reduced to around 2V offset, even when the trimmer is adjusted all the way. I checked that the trimmer resistor is the right one (w104). How can I debug this further?

[Synthbuilder]

I only get it reduced to around 2V offset, even when the trimmer is adjusted all the way.

Possibly one of the diodes, D4 or D6, is around the wrong way.

But also check that both 10V reference voltages are at the correct voltage. The easiest way to do this is to measure the voltage, with respect to 0V, on either end of the trimmer's pins. One end should be +10V and the other -10V.

Seems to be one thing not working properly - channel one doesn't go to the MIX output.

Check that the wire link SLV1 is fitted to the 'slave' board that handles channel one and two. Also, make sure that pin 4 of HDR on the slave PCB is connected to pin 4 of HDR on the master PCB. If not the IDC cable may not be seated correctly.

Tony

[kdjupdal]

Thanks for your help!

I found both the mistakes:

1. The VCA-X had a problem with bad connection. It was the MTA connector - I find one has got to be careful that the connection is good. I even have the "T-tool". I wonder if this is the best connector to use for self builders.

2. The VCA problem was indeed a diode the wrong way. Not D4 or D6, but the D8.