Another Supro... model 88T

[EFK]

I was going to try lifting the cathode cap but was poking around trying to trace out the circuit and ground it at various points and stumbled on the quick kill w/ pin 7. I think you are right - I think there is a circuit leakage or lead dress issue here, but it's such a mess in there the way those things are wired, there isn't much room to try moving things around very easily. I noticed if one or two of the wired come near the .01/.02/.02 series of caps, or at the least that tag strip, the noise gets louder. I replaced those caps, though, so they are all new. Something else that is really weird is the intensity pot (I put a new one in there) - as I rotate the pot from one side to the other, there is a point where the hum gets louder, then right near the end goes almost silent. NEw pot so can;t figure that one out, although the intensity pot is right next to the pilot light which is wired across the AC line.

I mentioned earlier I was going to try splitting the pin 3 cathode on the oscillator tube away from the V2 pin 3 cathode as it is shared w/ the cathode on V2 (the schematic shows this); I tried it, but while the trem no longer works, the throbbing is still there. So, apparently the trem works by feeding a oscillating signal back into V2 maybe? What I've done is wired up a switching jack as the footswitch jack so that when there is no footswitch plugged in, pin 7 grid is grounded out and everything is silent, or I can plug the footswitch in and switich it on and off that way. This works well, but I know it's just masking an underlying problem.

I can get a hair more gain and volume if I pull the oscillator tube anyway, so I probably will just forego the trem altogether.

[EFK]

While I still don't really understand trems, I think I know what the problem is. The pulsing hum is much worse on channel 1, which coincidentally, is getting its plate feed for V1 pin1 from the same tag as the plate feed for the trem tube pin 1. And, there are no filter caps anywhere in the preamp through PI. I'll bet if I could decouple those plate feeds, or get a filter cap in there somewhere before V1, it would stop it the right way rather than just band-aiding it like I have done. Am I way off?