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May 04, 2004, 08:01 PM
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PC Power Supply 12 Volt Maximum Mod ??

Would like modify a few of my spare 200 and 300 watt AT-ATX PC switching type power supplies to produce 17 to 18 volts, regulated, probably from the 12 volt, >10 amp DC out-put leads.....Anyone know if it's possible to up the 12 volt circuit this much using a few internal componet mods like perhaps the watchdog output monitor circuit zener or resistors ??.....I have very little experience with 'switcher
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May 05, 2004, 03:37 AM
Registered User
The turns ratio of the switching transformer determines the outputs....It is unlikely that you will be able to "up" the output much above 15v from the 12v rail even by tweaking the internals.......That aside the, the piv rating of the diodes then becomes an issue too....the original didoes have a piv of around 40v, you can expect to see voltage spikes in excess of this if you succeed in cranking the output up...

You could try and rewind the transformer.....! (not for the faint hearted )
May 06, 2004, 03:59 AM
We want... Information!
Bruce Abbott's Avatar
You could use the +5V and -12V outputs together to get 17V. The -12V output can only deliver a small current, but it is usually derived from the same windings as +12V. Therefore, you may be able to boost -12V output current capacity by replacing the rectifier diodes and smoothing caps.

Here's a couple of links that might be of interest:-

13.8 V / 15 A from a PC Power Supply

200 Watt Modified PC Power Supply 13.5 Volt 14 Amp.
May 08, 2004, 05:21 AM
Registered User
I have a magazine article describing this procedure in detail. It is based around an AT supply. If you are really keen to do this let me know, ill scan it for you.

May 08, 2004, 01:23 PM
Sorry for my poor English
biors's Avatar
i dont know if you can understand french, but sometimes pictures can helps, here is a link to a french site on how to transform an AT/ATX PC power supply into a 12V supply for our chargers.

AT supply have few powerthan recens ATX but are easier to transform, ATX needs to apply a "virtual" charge (light bulb in ex) before giving 12V out.

Good luck, those alims rocks for a very low cost.

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