HT-40 Bias Question

[Evil Z06]

Hey guys today I biased my first amp and it was my brothers Marshall and it was very easy.Now I want to do my HT-40....I have a question...which resistor do I use to measure the bias and what mA's should the EL34L tubes be set too? I also want to check the plate voltage and where would the best place to test this? Thanks

[thephantum]

I just use a bias probe, which inserts a 1 ohm resistor between the cathode (Pin 8) and ground. If your ammeter is accurate enough, you should be able to measure the bias current there.

Plate voltage is measured at pin 3. I would use pin 8 as ground.

There is no set number for bias. Anyone who tells you there is doesn't know what they are doing. Since you are measuring plate voltage anyway, just do the math.

[Evil Z06]

Thanks for the info...Would it be possible to show me in this pic?

[thephantum]

You need to take the measurements at the output tubes. The slotted "key" at the base of the tube sits between pins 1 and 8. The rest is academic. This would be the layout on the output sockets from the bottom of the PCB (from the top it would be reversed, obviously).

[Evil Z06]

Hello I tried to check the plate voltage and to bias the HT-40 and could not do it.Just before I tried it I did 2 more of my brothers Marshall's and they came out great but this Blackstar puzzles me.In the first picture I tried to touch the T10 and T18 bias point and nothing happened.Is this how you do it?
To get the plate voltage I tried what you said but I must being doing something wrong(confused) In next picture could you point to where I need to take the measurement? Thanks for your help I really appreciate it.