Henry 2K4

[redlght]

Has anyone ever strap grounded the grids on one of these amps and modified the the tap point for the grid current meter? I am thinking that grabbing the return on the filament center tap between R10 anb C52 shown by the blue line would get it to work again after the grid grounding.

 

[nomadradio]

Traditional shunt resistor for a grid-current meter is connected from B-minus to ground. But that assumes that the B-minus "floats" and connects to the filament center-tap, maybe through the relay and a zener diode. This model connects the B-minus to ground, more or less. At least the power-supply diagram shows the positive pole of the plate-current meter is grounded. Traditional designs "float" the B-minus, connecting it to the cathode transformer center tap, maybe via the relay and a maybe zener diode. Only the grids connect to ground, and the grid meter reads voltage drop across a shunt resistor from B-minus to ground. Don't see a way to bodge this into that power supply. Looks to me like you're stuck with the grid-resistor array unless you redesign the power supply. The overload relay is a part of this picture, and it would have to get rewired as well.

Looks like a can of worms to me. Not attractive unless you're going fishing.

73

 

[redlght]

What if i do this:
Instead of connecting the ground straps directly to the chassis, connect them to a single common point like adding a resistor say 1 ohm 10 watt from grids to ground reconnect the meter to that point on the ungrounded side of that resistor to use as a sampling resistor for voltage drop?