Low E Buzz

[passfan]

Can overloading an output transformer cause the lower notes to buzz at higher volumes ? I'm using an older Stancor and the amp is buzzing on the lower strings at higher volumes. It's worse when I change the impedance to 16 ohms from 8. I can turn back down and everything is sweet but if I get on those lower strings it comes back. Higher strings are fine. Could I be overloading the OT with the transients?

[jelle]

Depends on the buzz. hard to say from the post...

What is the filtering like?

[passfan]

2-100uf in series. 1-47uf , and 3- 22uf

[jelle]

Should be enough.

Pics? topology?

[passfan]

Topology is a Rocket. Someone busted the center pin off the rectifier and then just started plugging her in to see what would work. Had to replace the PT as it had a winding shorting out under load. I'm not sure which one as I dont have a megger. Its like i have a fuzzbuster going over top of the original note. I wonder if my bias cap is gone on the output tubes.

[jelle]

Sovtek rectifier tube?

[passfan]

No, vintage old stock. I'll try another one though.

[jelle]

Hmmm, several things could have taken a hit. Ecaps...tubes. transformer.

[Structo]

How about the OT?

If the rectifiers shorted and the B+ on the OT did something bad, could be some bad windings.

[passfan]

Changed to a different OT , same problem. Put a blocking resistor after the volume , no change. Scratching my head over this one.

[jelle]

Swap the ecaps....?

[passfan]

swapped to the main 2x100uf from a single 80uf. Haven't touched the others. Get no hum whatsoever out of her. Quiet as a mouse with no guitar. Touched all solder connections with iron. Changed out some components. Redoing the PI to blocking resistors now. Should have it back together in the a.m. This build always seemed to have more gain than the others I've built just like it and I don't know why. It may have had this problem brewing before the "accident". Voltages compare to others as well. B+ is high, up around 445. Different PT was higher

[jelle]

What happens if you scope it?

Where does it start?

[passfan]

Don't have a scope. Tried to locate it by dropping the gain through the preamp with a 12au7 but it was too hard to tell when the gain drops it disappears. I think it's in V1

[Gaz]

What about making a simple signal tracer? All you need is a probe, a high voltage blocking cap, and a potentiometer. I built mine into a little box, and run it into a small HIFI system. Truth be told, I have't used it since I got a scope years ago, but it did help me track down some distortion before I had one.