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RE: Tube voltage doubler

Posted by Eli Duttman (A) on May 2, 2016 at 11:58:45

In Reply to: RE: Tube voltage doubler posted by Vincin on May 2, 2016 at 10:50:19:

I came up with that 100 muF. value, after perusing a 5U4G data sheet. A 40 muF. part is given as "typical" in the commonplace FWCT setup. As the inrush current limiter provides a margin of safety, I opted for 50 muF./5U4 plate.

Using 100 muF. caps. in the stack of a "full wave" doubler is equivalent to 50 muF. in a FWCT configuration. Cap. generated "hash" should not be beyond your choke's suppression capability.

When really big caps., like the 820 muF. parts found in a "McShaned" H/K Cit. 2, are in a doubler stack, I favor inserting a "hash" filter LC section made from a high current RF choke and a 1000 pF. mica or NPO ceramic cap. between the doubler stack and the main filter choke. Here, RF energy that could pass through the main inductor's winding capacitance is a matter of concern.

BTW, a "hash" filter is never a bad idea. Even if cap. associated noise is not an issue, suppression of garbage riding on the AC mains can only help the cause.

8X Mouser stock # 647-LGN2H101MELZ40, plus voltage equalizing resistors, would make a suitable doubler stack. That part is less than 1 inch in dia. and less than 2 inches tall. Perhaps mimicking Sheldon Stokes, by etching a PCB for those caps., would be a good idea. S/S frequently engineered his cap. PCBs to mount on stand offs attached to power trafo hold down machine screws.


Eli D.

• 5U4G Data Sheet   (Open in New Window)

Edits: 05/02/16

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