pentode to UL conversion?

[whoaru99]

Simple as pulling out the g2(?)100 ohm resistor connection to B+ and connecting the UL taps in place?

 

[jaymanaa]

Yes, but the OPT in your diagram does not have UL taps (but you know that). There is also much concern as to where the UL taps connect to the windings; 20%, 30%, etc... Personally I like pure pentode with SS regulation on the screen voltage. It's all basically a question of where you get the screen voltage and how much of it you get. A completely separate dedicated, regulated supply is the bomb. IMHO

 

[whoaru99]

Yup, UL taps aren't shown on the schematic and are not currently used. They are present on the OPTs though and are 40%.

 

[Tom Bavis]

Wouldn't hurt to leave the 100 Ohm resistors between the screens and UL taps, though 6L6s may not need them, as higher transconductance tubes may. Actually will be easier on the tubes (hope they're 6L6GCs...), but may cost some max power.

 

[gadget73]

If you really wanted to get fancy about it, you could install a switch to flip it from pentode to UL. for extra fancy points, make it a 3 way to switch it from pentode, UL or triode mode. You'd just want to make sure that the cathode resistors are in a range where it runs reasonable bias levels in all 3 modes.

 

[whoaru99]

Actually will be easier on the tubes (hope they're 6L6GCs...), but may cost some max power.

I'm using Phillips/ECG 6BG6GA with adapters.