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Can you make 0-5V DC out of 2.5-0-2.5V AC

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Yes, it's a 300B filament supply. At this moment I'm using 0-14V AC to get 0-5VDC and that gives quiet some heat. And because the 2.5-0-2.5 was still available when I used AC I thought I might be possible ... but I'm afraid voltage will be too low to use a regulator. My 300B draws 1.41A @ 5V.
 
Ralph,

Where is the 2.5-0-2.5 coming from?
If it's from an enclosed transformer, that you can't overwind, there are other solutions to "find some volts".
If you buy a small (15 or 30VA) toroid, you can hand wind some turns - perhaps 3 turns per volt, to put in series with the existing, to make the exact voltage required.

Sorry for the long rambling English. I'll clarify if you're interested.

Cheers,
 
Ralph,

If you are using a regulator, there is another way to reduce it's heat dissapation: You should reduce the value of the resovoir (smoothing) cap. This will increase the ripple to the regulator, and thus reduce the RMS voltage and the power. You must be careful not to reduce it too far. The voltage at the bottom of the ripple must still be enough for the regulator to operate correctly.

If you haven't got a scope, you can use a multimeter on AC range to check the output DC for ripple "break-through". Keep reducing the cap until the ripple breaks through, then go back one step.

Cheers,
 
Hi moamps

If your secondary 5V is unused, connect them serial and out of phase with 14V secondary. You will get 14-5=9V AC on bridge. Strange idea but works.

Interesting but I don't fully understand yet :scratch:

I have two secondaries, 2.5-0-2.5 and 0-14V. Let's give them a letter for identification.

wire A: 2.5V
wire B: 0V
wire C: 2.5V

wire D: 0V
wire E: 14V

Which wires should I connect together now?

Thanks very much,

Ralph
 
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