• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

screen tap on OPT

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hirafu_boarder

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Joined 2007
#1
Please excuse my inexperience with output transformers.

General question:
With regards to a single ended OPT with multiple primaries, could one of the primaries be used as a screen tap?

Specific question:
I have OPT with 0 2.5k 4k 7k 10k primaries (and 0 4 8 16 secondaries).
If I use the 7K for B+, can the 2.5K tap be used as a 35% (2.5/7) screen tap?

Thanks!
Jeff
 
#2
If the transformer is of a suitably high quality, with very tight coupling between the primary sections. Otherwise you get HF phase shifts and your output stage may turn into an oscillator. You can run pentode-mode into any old transformer, but UL demands high quality (which probably means an OPT designed for this purpose).
 
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