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Old 20th May 2004, 03:20 AM   #1
zobsky is offline zobsky  India
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Default SS power supply question

aarrgh

i feel much better now.

anyways, .. while wiring up a 12b4a preamp (seem to be a lot folks working on that these days), .. i just realized that my power tranny was spec'd at 250-0-250, .. instead of 250 across both the secondary windings as indicated on the transformer wiring diagram.

i plan to use a SS rectification scheme with a damper diode at the end of the CLC filter to give me slow start (BTW, .. do damper diodes cause much tube sag??).

this wouldn't be a problem if i used 2 SS diodes in a full wave rectifier as in http://members.tripod.com/~gabevee/mypwrsup.html (section = "a solid brute" ) , .but i, in all my innocent wisdom, already wired up the power supply using a SS diode bridge (4 diodes).

i can always rebuild the PS, but before i do, .. is there any reasonable way to get 250V usng the bridge supply?

also, from the link, are the resistors really necessary in practice and if so, what should they be valued at ?

of course, i could just use a tube rectifier, such as a 12ax4, .. but that wouldn't be any fun, ..would it?

thanks
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Old 20th May 2004, 03:58 AM   #2
SY is offline SY  United States
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Sure. Just use the positive output of the bridge. The negative output can just float, or if you're ambitious, can power the bottom of a cathode follower.
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Old 20th May 2004, 08:14 AM   #3
SHiFTY is offline SHiFTY  New Zealand
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Just rewire it as a fullwave rectifier. Will take you all of 5 minutes.
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Old 20th May 2004, 04:28 PM   #4
zobsky is offline zobsky  India
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Quote:
Originally posted by ShiFtY
Just rewire it as a fullwave rectifier. Will take you all of 5 minutes.
unfortunately, .. this is a integrated bridge rated at 1000PIV , .. so i can't (or don't know how to rewire it as you say


no biggie, .. i can always buy a couple of diodes and build a fullwave rectifier, .. but that will have to wait for the weekend


BTW, .. can anyone comment on the value (ohm / wattage) of series resistance to use, as per the link i mentioned. my operating parameters are 50mA draw at 250V . perhaps a pair of 100 ohm resistors??

as for the caps across the diodes, .. a pair of cheap micas should do it, i would think
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Old 20th May 2004, 04:48 PM   #5
SY is offline SY  United States
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Quote:
i can always buy a couple of diodes and build a fullwave rectifier,
You don't need to- read my post above.
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