Hiwatt 200 (DR201) bias pot + general questions

[boroman]

Unfortunately I can't measure more than 375V anywhere on the tubes - might be diodes failed in power section?

[Helmholtz]

What do you measure at the CT of the OT? What is your heater voltage?
What is your mains voltage? Where is "boro"?

[boroman]

I think everything's OK:

I may confused PIN2 and PIN3 with PIN3 and PIN4 because they are written between the pins, not "at the pin".
But there's another case. I was told this amp is CLASS B amp. Could not find any information how I should bias Class B amp? Is the calculation the same as AB? At the moment tubes have got like 18-20mA each. Form the 70% safe plate dissipation rule, with 680v it would be 25mA... so 18 is a bit cold? But it may be Class B that is set differently?

[Helmholtz]

We still don't know your actual screen and plate voltages.

The TFK EL34 datasheet recommends for what they call "Class B" 30mA@ Vp=500V/Vg2=400V and 25mA@ Vp=800V/Vg2=400V. If you measure cathode current, add 4mA for screen current.

[boroman]

Thank you,

Screen 375
Plate 680 (720 when off standby)

(I wrote those on the pic)

[Helmholtz]

(I wrote those on the pic)

Oh, I see.


Still wondering where Boro is. Indonesia?

[boroman]

Still wondering where Boro is. Indonesia?

What does it have to do with the topic (that you ask 2 times)? Lithuania.

[pontiacpete]

I think Helmholtz just wants to know what voltage AC is used in your country. Post #17

[boroman]

I didn't get it, sorry. Felt a bit offended. Wall voltage 235-238V here.