Ok so hold that thought.Smokebreak wrote:Problem stays with the socket on tube switch.
Essentially no current flowing from the grid or from the coupling cap on either side, so this is good.Smokebreak wrote:Martin, I'm a little confused. Reading across the 100K bias feeds reads negligible V drop(~.01v), but that's because there's no current in the grids right? Reading straight from grid to cathode, with the 1Rs in reads the -65V bias voltage.
I think I'd leave the ground scheme as-is, and just measure across the 1R's to get mV (numerically = mA).Smokebreak wrote:I've never used the shunt method, and I'm skiddish about learning the process on this amp.
So the chassis ground is indeed at the input, so the ground wire from the main board only connects OT, cathodes, and last capcan grounds to the ground network on the board, on the other side of the reversed diode.
So if OT, capcan is connected to cathodes, and cathodes go 1R straight to chassis, I should be fine floating that board ground wire eh?
Cbass is talking about using the OT primary resistance in the same way as the 1R cathode resistors (measure voltage across each half of the OT), except you have to do some math. That's a very good way to get plate current. The shunt method is setting the meter for current and shunting each half of the OT primary with it to read current directly. This is a bit risky because if you slip you could short B+ to ground and blow the fuse in your meter.
Going back to the top, you may have a socket problem. Did you try to clean and retension the power tube sockets? One more thing, do you have the same screen voltage on each side? Maybe a screen resistor has drifted.
That's (old fart) why I wouldn't own one, but I might make use of the tone stack some day…..
