Blackface Deluxe Reverb No bias current reading

[Bassisst90]

I have this blackface deluxe reverb that I'd been working on (replacing screen grid resistors, filter caps, and the like) and I went to start it up to bias the amplifier using a hoffman bias checker. The lamp did not turn on (have no clue why), the power tubes glow, and when I take it off standby the current reading always states 0ma. It makes all sounds indicating that its on though (speaker pops). Anybody have an idea whats wrong?

[km6xz]

I do not know what a hoffman bias checker is but with it not in the circuit, and the tubes in their sockets, does it still not work? Measure the plate voltage screens and control grid with a voltmeter. That will tell you what is happening. The plate voltage is missing, the cathode ground connection of broken or if is biased with a high negative voltage that is cutting off the tube. What does it measure at those points?
If it works with the bias checker removed, there is an open in the cathode lead of the tester. If it was used on a amp with shorted tubes the cathode resistor in the tested could be open. They work by inserting a small series resistance in the cathode return line to ground. The device, if it is like all the others, measures the voltage drop across that resistor to get a idle current value. If it is open, you would get a weak pop from the speaker but no sound and no cathode current.

[g1]

Info from the Hoffman site says this bias checker has no cathode resistor. It requires your meter be set to DC milliamps.
If you have your meter set to DC mA and have the probes in the appropriate meter jacks, your meter may have a fuse for the mA mode. Make sure it is good.
As far as the lamp, if the tube heaters light up, then the lamp must be bad or the lamp socket connection/wiring.

[km6xz]

Too bad that it uses test leads instead of a shunt, accuracy will not be as good since any series resistance will impact the reading and actual current flow more than if the high z of the voltmeter function is used on a shunt. It is also not as safe. Better modify it to a shunt type circuit.
Anyway measure the voltages without the checker in the circuit and report the values.