Yeah I got James OPT and a choke
1 x JS-9612-2
2 x JS-6123HS
1 x JS-10-200S
Hmmm how can I use the unused 6.3v for a buck? I took a picture of the PT's diagram.
Thanks.
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Yeah I have all the transformers and tubes
I'm also thinking about Damn Good 300b but I think i will go with Tubelab SEI think it would be best to just use a separate transformer as the buck winding, assuming that you want to go the buck route.
After I posted my comment about using an unused secondary as the buck, I had some second thoughts about whether it would work, since all windings share a common core.
Tonight, I ran an experiment. I set up a small transformer on my bench, and fed it line voltage from a variac with a kill switch to be cautious, and used one of it's secondary windings to buck its primary. Measuring the voltage on another secondary, I was able to get both buck and boost, depending on how I connected it.
Specifically, I was measuring the 6.3 ( nominal ) secondary, which at full output from my variac produces 6.6 volts. Using a 5 volt secondary on the same core as the 6.3 volt winding, I was able to buck to 6.3 volts, and boost to 7.0 volts. So, it seemed to work about as expected, but I didn't try it under load, which might change the result.
Still, filament transformers are cheap, so there is no reason to do it an unconventional way. Just use a separate transformer - that's the safe and well established way of doing it. Others with more experience might have some better information or experimental results.
Win W5JAG
After I posted my comment about using an unused secondary as the buck, I had some second thoughts about whether it would work, since all windings share a common core.
Tonight, I ran an experiment. I set up a small transformer on my bench, and fed it line voltage from a variac with a kill switch to be cautious, and used one of it's secondary windings to buck its primary. Measuring the voltage on another secondary, I was able to get both buck and boost, depending on how I connected it.
Specifically, I was measuring the 6.3 ( nominal ) secondary, which at full output from my variac produces 6.6 volts. Using a 5 volt secondary on the same core as the 6.3 volt winding, I was able to buck to 6.3 volts, and boost to 7.0 volts. So, it seemed to work about as expected, but I didn't try it under load, which might change the result.
Still, filament transformers are cheap, so there is no reason to do it an unconventional way. Just use a separate transformer - that's the safe and well established way of doing it. Others with more experience might have some better information or experimental results.
Win W5JAG
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