No current draw on a tube preamp stage.

[Anthon]

This is a 5F1 champ I've built. I already got it working, but then I decided to clean up wiring, change grounding etc...
And now it doesn't work anymore.... all I get is a quite hum.  :-\

It must have something with the first stage not pulling any current. I get no voltage drop on the bias and plate resistors. The other stages have correct bias voltages.

The things I already did:
- I tried different tubes.
- I replaced the tube socket (one of the terminals was messed up anyway).
- continuity meter shows no problems in the preamp area.
- I resoldered all the relevant joints, just to be sure.
- the bias resistor is grounded by a thick copper wire to the chassis.
- I tried disconnecting the bypass cap (in case it leaks).

Not sure what else I can do... any suggestions?

P.S.: I built the cabinet from scratch  8)

 

[PRR]

Heater not heating up.

 

[Matt Nolan]

Yes, check the heater. I find with tube builds it is always useful to have a dummy tube for the first power supply / wiring test. Get a plug that fits the tube socket and solder in a resistor for the heater and a resistor for the anode to cathode path. Then you can check voltages, infer currents, etc.