On Jun 4, 4:11*pm, JIMMIE wrote:
On May 29, 8:23*am, JIMMIE wrote:

I want to replace the vr 0A3 tube used in the bias circuit of a 6146B
amp with a 75V zener string. Can I just directly replace the tube with
the diodes or *will I need to make other modifications to the circuit?

Jimmie

Thanks all, problem turned out not to be the tube. still not
absolutely sure but *it was either the bias pot or a cap. I'm fairly
certain I changed out the cap about a year ago so best guess is the
pot. What I am thinking was happening is the pot was opening up
sending its share of the current through the tube overloading it with
about 90 ma of current causing the tube to arc. Should have just
shotgunned the circuit from the beginning.

Jimmie


hey OM

The dead give away should have been the series resistor to that OA3
heating up big time since P=I^2R the current doubled, the power
quadrupled that resistor would have could have let its' smoke out.

73 OT
de n8zu