I'm building a trem using an MV-53 LFO and, essentially, the audio path from a Tremulus Lune. I've got it passing sound, but I've run into two problems. There is a 10k (or there about - actually closer to 9k) oscillation in there somewhere, and it is bleeding through the power supply to the analog audio path. The LFO and the audio path are on separate boards, and the only points of contact are the 9V, the ground, and of course the LFO's output, which has a separate ground connection, and is of course optically isolated from the audio path. When I run the LFO and audio off of separate power, the oscillation goes away, so I'm assuming that is where the problem is coming from. BUT, when I tried to isolate them with a resistor, the audio path stopped passing audio. So, and suggestions on getting rid of the oscillation? Altering the ground scheme didn't help, only powering it from separate batteries.
The other problem is that the depth control (identical to the one seen
HERE) cuts out at the middle 1/3rd to 1/2 of its range, or rather, when the depth control is in that middle range the audio cuts out. I've looked at the output of the LFO on my oscilloscope, and the problem is NOT in the output of the LFO - the LFO out goes up and down exactly the way it should, but for some reason by the time it gets to the other side of the opto (VTL5C2) it is cuts out the audio completely. I've tried different values of load resistors on the opto, and there doesn't seem to be any change. I've played with the various trimmers, and it doesn't help. I've also replaced the pot, to no avail.
So, any suggestions on the next trouble shooting step?
Gabriel