OR80 w/140 OT

[VintageJon]

I have an OR80 with a bad OT, Output Transformer, in the shop.
Orange UK recommended a 140 OT as the OR 80 was out of production.

After installing it and making allowances for the 4 X EL34 VS.
2 X EL34 impedance differance I find a very non-symetrical waveform
from the output. Power is very good but it clips the negative going side before the positive going side. Cross-over distortion notch
shows up high on the positive-going side rather than in the center,
zero-line, of the waveform. Same results if I have input to the effects loop, (reverb return), or the input.

Any other experience with this problem?

Jon
[email protected]
Austin Texas

[Gladmarr]

VintageJon,

I'd say you have a defective OT. It sounds like the primary on that OT isn't symmetrical or something. Are your plate voltages the same out both ends of that primary tap? It may be something more complicated than that. You've probably already tried that check anyway. The other option is to get a better OT. I know there's an axiom transformer that is supposed to be an Orange replacement.

http://www.mercurymagnetics.com/axiompricing.htm

I don't know if that helps, but I tried right?

Gladmarr Audio Laboratories

[Gladmarr]

...on second thought, have you checked the phase inverter circuit? I have an Earth amp here that I've had that same problem with, asymmetric half waves on the output and one side clipping before the other. Check caps in the PI and see if you're getting a symmetric output from there.

Okay, now I've tried some more, that should either help or I'll look like a tremendous dork.



Gladmarr Audio Laboratories

[VintageJon]

Gladmarr- IT definetly originates in the Phase Inverter. Thought of
"balancing" it- but he like the way it sounds. "If it's what the customer wants, don't change it!"
Thanks for your post.

Happy New Year,
Jon