Tube Amp Archive

That does help. Thats exactly what I was thinking. I've been having trouble wrapping my head around why the isolation transformer will work. Currently I have the chassis grounded, this in, effect shorts one of the prongs (hot or neutral depending on wiring) to ground causing the amp not to function....

i see what youre seeing in the schematic.

But,
i think that power plug current is still passing thru the chassis. see the heater circuit.

I think a 1:1 transformer is needed at the plug, such that the chassis can be earth grounded.

I don't think they did. They have a step down for the speaker and a high tension for the tubes. There's no isolation transformer. What i'm curious about is if i throw an isolation transformer right where power comes in, and i leave everything wired the same, can i still earth-ground the chassis? I t...

Just wanted to post a little bump. To recap (no pun intended) this amp has the heaters all run in series and connected directly to the power plug. one side of this circuit runs through the chassis. When you ground the chassis to earth, the amp doesn't work! you've shorted the heater circuit to groun...

Thanks for the info.

I don't see how this makes things safer.

can someone explain?

and what model isolation tranny did you get?

thanks everyone!

true, I wired in a fuse and put a 3 prong plug on the amp. Knowing full well that an improperly wired outlet could screw me.... I could take that leg of the transformer off the chassis and and wire it discretely, but then what is ground? someone else told me to put a 1:1 transformer, and that would ...

I'm into safety.

I don't see the danger in the heaters. I can use a 1:1 transformer there.

I think the problem is that one side of the HT transformer is going thru ground. but I could isolate that but i'd need some kind of isolated 1/4" jacks, right?


kinda confusing!

as the amp is now, it doesn't work in a grounded outlet because the chassis is grounded.

I could discretely wire the heaters, but still that wouldn't fix that problem.

Hey guys, I recently got a free Kay 703C... http://www.freeinfosociety.com/electronics/schematics/audio/kay703c.pdf I recapped the multi-section capacitor and replaced the non ceramics with orange drops. I also added a grounded plug and a fuse. The fuse and power switch are coming off the black wire...