Hi, I am trying to rig up a fixed bias stereo 807PP amp using diode
rectifiers. I have wired the amp so that negative bias/g1 voltage is
switched on with the filaments, and then the B+ and screen/g2 voltage is
turned on with a second (standby) switch.

With roughly 550V on the anodes, 295 on the screen (g2) and -33V on the
grids it works fine, solid AB1, no problems.

The problem i encounter is turnon surge of the bias voltage: When I turn the
B+ on, the grid voltage briefly rises from -38V to -10V before settling back
to -33V. As a result, the plate current of each 807 rises to about 100mA at
turn on, settling back to 35mA. This is pretty high, and I am a bit worried
about the cathode stripping effect of this! The 807s are NOS and it happens
with a different (good) set as well.

My bias supply is like this: 100VAC secondary winding - 1N5404 - 220uF -
2.2K - 22uF - variable resistor to ground (bias taken from wiper). The
other leg of the 100V winding is connected to ground. I can adjust the
current quite nicely, it works fine, just the massive turnon surge.

I am guessing I need better regulation in this bias supply, anyone got any
schematics for this type of thing?

Cheers for any advice
Henry