+12, +6, -6, -12V Power Supply

I am trying to powr an old test instrument with a dead supply.

What would be the most straightforward way to make a regulated DC power supply with the following four voltages plus earth reference?

+12V +6V

0V (Earth reference)



250mA per rail, eg. 1A total

One possible option might be to use a 1A 12VDC regulated plugpack, and build from there. I assume that would eliminate the need to regulate the remaining three voltage outputs separately.

Thanks for any suggestions.

David King

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David King
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Most straightforward? Four of these:

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and a sixteen-pack of alkaline D cells. (or four four-packs, etc.)

Wiring the assembly appropriately is left as an exercise for the student. ;-)

Cheers! Rich

Reply to
Rich Grise

A power supply with +/-12VDC output and a couple of linear regulators (eg. LM317/LM337) and a few passives would be pretty easy. If the current drain is really 250mA per rail then it will dissipate an additional 3W in the regulators (1.5W each), so they'll need small heatsinks.

If it's a sensitive instrument you might need to pay attention to the quality of the supply (for example, ripple on some or all of the rails).

Best regards, Spehro Pefhany

"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Spehro Pefhany

you could power it with a 12V AC wallwart and make the dual supply with a full-wave voltage doubler, lots of modems use an AC wallwart I assume that is what they do


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I would go for a +/- 5v regulators a diode voltage drop above ground.

Unless you can get a LM7806

and a 7906

Mouser also has OnSemi 6 volt regulators.

I think the +/- 12v would be trivial.


Reply to
Martin Riddle

[+/- 12/v, +/-6V]

If you can find it, a suitable transformer with 24VCT and

12VCT windings will suffice; ground the two center taps, and each of your four supplies consists of two diodes, a filter capacitor, and a three-terminal regulator. DigiKey lists a Tamura PFT24-28 for a little under $30 that'll do the transformer part.

If you prefer to use prebuilt modules, though, it'll take a lot of catalog search. It's more likely you'll find

+/- 12 and +/- 5V (and shockingly high prices for off-the-shelf).
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Fix the dead supply. Be like Frankenstein, bring it back to life...

Reply to
Fred Bloggs

+/-12v is easily mad with 7812, 7912 and a 12-0-12 iron, or just a 12v wind and half wave rec. +/-6 is easily made from those rails with 2 more 78/79 regs.

Or if 5v rails are adequate, just use a pc psu.


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That's 'Fronkensteen'.


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