I have the great honor of being entrusted with a Schumann PLL for repair. I've also taken the time to trace it. Despite the goop, and rats nest wiring which prevented me from using my camera to trace, I present my hand drawn papers of this piece of vaporware.
Keep in mind that the board drawings are of the trace side, so the IC pin numbers have to be mirrored.
I didn't mention on the board 1 page that the 240R, 120R, 110R, the cut 10K, 1M, 200K, and 150K are metal film. All the others are carbon comp.
I don't get the cut 10K resistor. I triple checked it, and it's as drawn. I suppose that maybe 10K here, and a jumper where the 200K is wasn't cutting it, so he filled it in with solder, and cut the resistor lead. It is what it is.
There's also an Appegiator jack, and a Drone jack, though neither is wired inside. I don't know how the Appegiator would work/connect, and maybe that's what the SIP sockets on board 2 are for. A drone signal could be easily injected though. I've been looking at the Drone Lab II project. Easy build, tunable, and would perform the tasks of the Schumann drone quite well. Not really a blip on the radar right now.
Unless someone beats me to it, I'll be transfering this to TinyCAD soon, and after breadboard verification, to vero thereafter.
This box is something else.
The voltages measured in that were +/-10.3, though that's still well over the 7V max operating voltages.
