Using Screen Grid tap on OT for Plate?

[Pdavis68]

I have this output transformer.

It says the screen grid tap is 33% of the plate tap and I was wondering if I could use the screen grid tap as a 5K tap on the plate. I'm doing a little 5W SE build. I have 2 OTs I can use (one with the two taps and one with just a 7.5K tap) and I'm considering the possibility of a switch to go from ~300V at the plate to ~250V at the plate for reduced power.

[pdf64]

It's usually 33% or whatever of the winding, rather than 33% of impedance.
Best to ask Triode, or measure it, ie check the voltage ratio.

I'm considering the possibility of a switch to go from ~300V at the plate to ~250V at the plate for reduced power

It doesn't tend to work like that; Vdc dropped across the OT primary is negligible.

[Pdavis68]

33% less winding would work out to 33% less impedance, wouldn't it?

It doesn't tend to work like that; Vdc dropped across the OT primary is negligible.

I was going to use a 3PDT to switch the transformer winding as well as plate, and screen voltages at the PS. But I'm having second thoughts about that now, at least for this build. I'm doing a ghetto build using a computer PS as the chassis, so space is tight.

[pdf64]

The transformed impedance is related to the square of the winding / voltage ratio.

[Pdavis68]

Ah.. Stupid math.. lol. Okay, well, I'm going to use the 7.5K transformer with just one tap for this build. Like I said, tight on space. Not enough room for the additional switch and all the wiring that would accompany it.