by EWBrown » Mon Dec 24, 2007 9:33 am
In my small 6S4 SET, I use a heathkit 54-59 trannie (from an old TV color dot / bar generator) which has about 130 VAC winding with around 300 mA capacity (I could feed a 40 watt lightbulb with it delivering 120 VAC output) , and a 6.3 VAC filament winding around 4A capability.
FWIW, the original Heath circuit also used a voltage doubler, with 1960s vintage silicon rectifiers and 2X 100 uF can caps. Under normal operating conditions this delivered a B+ of 306VDC with about 50 mA loading. THe "hot" can cap was mounted on a fiber mounting washer, and the can was sitting around 153VDC (and yes, it could bite the unwary). In those days, safety wasn't a major factor... Not only did they not use a fuse in the AC primary circuit, there were hot can caps that were far too easy to come into casual contact. Yhe metal covers were a must, when using these, if one wanted to enjoy a long and healthy life...
I used a voltage doubler with this (same as in the "Abraxas" amp) with 2 uF4007s, two 470 uF / 220 V caps, then through a 15H choke, iwhich has a DCR of 411 ohms, nto a 100 uF / 450V cap.
Unloaded, the B+ is around 360VDC, and drops to around 300VDC with a total load of approx 55 mA (and and around 340V before the choke).
I also full-wave bridge rectified the filament voltage.
/ed B in NH
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