Switching a Marshall 50/100 from high to low power while on

[Littlewyan]

Well the valve would lose it's screen voltage for a very short amount of time. It still happens nonetheless. What is the effect of a valve losing screen voltage? I know someone on here recently forgot to hook up the screen grid and I vaguely remember the valve just drew a lot less anode current. Could be wrong though.

[pdf64]

Yes, plate current is controlled by screen grid voltage; without sufficient voltage to the screen grid, the plate current cuts off, eg I understand that a KOC preferred standby implementation disconnects the power tube screen grid supply.

[Leo_Gnardo]

Yes, plate current is controlled by screen grid voltage; without sufficient voltage to the screen grid, the plate current cuts off, eg I understand that a KOC preferred standby implementation disconnects the power tube screen grid supply.

Ampeg SVT Classic does standby this way too.

[gui_tarzan]

This one is ready to go. I ended up changing that power supply resistor, a fuse on the circuit board and V4's 1K 5W resistor because it was way out of spec. The rest all tested good as did the tubes so the guy got lucky and I bet he won't do that again.