Grid Biased power tubes with a Bridge recto and no bias wind

[JamesHealey]

Is it possible to tap a voltage off and switch it to negative voltage from an amp with no bias winding and a bridge rectifier?

it's gotta be possible somehow?

[rhinson]

Is it possible to tap a voltage off and switch it to negative voltage from an amp with no bias winding and a bridge rectifier?

it's gotta be possible somehow?

yes it is. you have to use a dc blocking cap off where the hv sec meets the bridge. look at this schematic for how:

http://www.schematicheaven.com/newamps/sundown_a50.pdf

obviously depending on your particular hv sec and tube compliment you'll have to adjust the first ground reference resistor----i'd suggest put at 100kl pot there to dial it in first so that you don't over bias while firing up the amp and then measure and go back and put in the set resistor----or just leave it in if you want rh

btw, i'd use a 1000v film cap here for the blocking cap to be on the safe side.

[JamesHealey]

Yeah i'll be using a 1600v polyprop.

It makes sense now looking at it why u'd use a cap there, feel stupid.

Should all be good now