On Sat, 01 Oct 2005 22:56:52 -0400, Jon Yaeger
wrote:

I'm contemplating using a pair of 6AU4GT damper diodes for a full-wave
bridge, with a 700 VAC CT tranny.

I assume that during an AC cycle the cathode will "see" -350 volts relative
to the heater which would normally be operating near ground.

And peak of (350) x (sq-rt 2) = about 500 volts (during startup,
and lower after warmup).


Looks like I'd be in trouble without floating the filament at a minus
potential.

Is that a real concern in this application? And if so, is floating the
filament a -300V (using SS rectifiers) a practical work-around?

Else would I be better selecting another device or topology?

I'd say that it's a non-issue, but if it bothers you, using
the damper diode as slow-start device following silicon
rectifiers may be more attractive to you. Serves most of
the same purposes, but not all.

Good fortune,

Chris Hornbeck