Schumann PLL Trimmers

[velouriafx]

Has anyone built Schumann PLL yet? How can I adjust trimmers using a DMM?

[Zanius]

It is marked in the layout. Adjust to get + and - 12 volts.  
If you mean how to use or where to put your meter to measure this, better try some simpler build :)

I've built the PLL with its add-ons and I have to say it was a quite frustrating build, took me about three months to understand, design and build.

[velouriafx]

Thanks for the answer. I've already built about 200 pedals from the site, but I was a bit confused with it for using AC. I was not sure if I should use the ground as a reference with the DMM. But I managed to regulate the voltages without problems in the end. The board is ready and apparently everything is working perfectly. I have not had time to test with caution yet.

I am using this lamp (http://www.soldafria.com.br/image/cache/catalog/olhodeboivermelho-500x500.jpg), but I am in doubt of where to connect the other wire. I linked to the Ground but it did not work. Probably have to link some point with V-, right?

I was very confused initially about the operation of the voltages in the circuit, but yesterday I analyzed the schematic calmly and did some tests and got to understand a little better.

[Zanius]

Nice! Yeah, AC was my primary concern too, as it was an unknown territory for me. Anyway, the lamp you have is prob for AC operation, but the "indicator lamp" cable on the board is after the bridge rectifier and should measure -12v DC. So, use a normal led, but take that cable to the cathode and ground to anode.

[digi2t]

Be careful when setting the voltages for the rails. If you're using an SN74HC14N H-S trigger, then avoid running over +/- 11.0v. The chip will not support any voltage level above 11v either way. It's actually rated to only 7v, but it'll handle up to 11v. It was used in some original units. You can use the MM74C14N, or the more common CD40106BE at levels around +/-12v.

Also, in all the original units (and clones) I've worked on, none were ever adjusted to perfectly opposite voltages. There were always deviations of about 0.5v between the two, i.e. -11.0 / +10.5, or -10.75 / +11.25, etc. With clones, I found that setting the voltages perfectly opposite never sounded as good as having a bit of offset. A bit of imbalance, one way or the other, always yielded better tonal results. Feel free to tweak the voltages while playing through it. There's no hard and fast rules here.

[velouriafx]

I used the CD40106BE.

I'm building the drone right now. Actually, voltage regulation is not fundamental.
I have not yet learned how to use the controls, but I have already been able to find sirens, bizarre pitch variations and many other things haha

[digi2t]

I have the original Schumann instructions, as well as a more detailed guide available here;

http://www.aronnelson.com/gallery/main.php/v/digi2t/Information/PLL+connections/