SS rectifier recomendations?

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SS rectifier recomendations?

Postby TerrySmith » Sat Nov 22, 2008 10:31 am

I plan on making up a plug-in SS rectifier for my MK-3's using old metal tubes to house them.

Will UF4007 diodes be enough? Can they be paralled for more current?

My MK-3s are new build (3 yrs ago), pre- Poseidon boards, SDS cap board, Triode transformers, CL-80 inrush limiter. I'm using 6CA7 large bottle EH's for outputs until I can afford to buy another pair of Sylvania 6550's. Bias is set at 55 ma per tube.
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Postby TomMcNally » Sat Nov 22, 2008 1:00 pm

Terry -

Diodes aren't normally paralleled for more current.
They don't play nicely together that way. It is common
practice to put them in series for higher voltage - I have
diode stacks in transmitters at work made of 1000 volt 1 amp
diodes that are good for 20,000 volts PIV.

In any case, the UF4007's are probably fine. Be careful to
keep the diodes well inside the metal tubes for safety,
you don't want to touch one with 500 volts on it !

Often people put a low value resistor in series with the output
side of the diodes as an inrush limiter, maybe 5 ohms at 5 watts.
You should be able to search for some info on that.
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Postby Ty_Bower » Sat Nov 22, 2008 5:36 pm

I'm not convinced a single UF4007 has adequate inverse voltage handling capability. My P782 is about 445 VAC from center tap with no load. The peak inverse voltage across the rectifier diode will likely exceed 1.25 Kv, which is more than a UF4007 can handle. Try putting it together in PSUD2 and watch the voltages.

I'd series a couple of them as Tom suggested, or use a part with a higher PIV rating.
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