Pc power supply questions

[roni21702]

I need a power supply that put out 24-28 volts dc and about 5-8 amps. I would like to know if I can modify a pc PS to get this voltage from it. Does any know how these work? I was thinking that I could trick the PS into giving me the power I need. Maybe change a resistor or something. Any information or help would be great. Thank you

[ger21]

http://www.cnczone.com/forums/showthread.php?t=17548

[unterhaus]

It's not likely that you can do this.

They are built as cheaply as possible. The way they work is that they rectify the ac voltage from the wall to DC, and then switch that back to ac at high frequency through a transformer. That voltage is rectified back to dc, compared with the desired voltage, and the error fed back through an isolated interface to the switching stage on the primary side of the transformer.

The nicer ones I've looked at recently seem to have multiple transformers and switching stages, older ones had multi-tap transformers. The feedback loop around the transformer can possibly be modified to increase the voltage, but you would probably have to rewind the transformers to get a significantly higher voltage. You would also have to make sure all the output components can take a higher voltage.

Not impossible, but there is a lot of electronics engineering expertise represented in a typical pc power supply. There is an old saying that engineering is the art of doing for a dollar something any fool can do for ten dollars. In this case that may be pretty optimistic about the fool.

[NC Cams]

GER21's link is one of many that will work for daisychaining PC power supplies. The user DID it and proved that it would work.

Some more PC based links are listed below:

Daisychaining ATX power supplies:

http://www.cnczone.com/forums/showth...015#post142015

http://forums.bit-tech.net/showthread.php?t=108208

If you STILL think it won't work, you can build a linear based one using the following link:

Linear P/S design/construction
http://www.campbelldesigns.com/files...ply-part-1.pdf


Unterhaus' comments pertain to modifying a PC P/S and I'd agree with him - don't screw with them outside of the daisychaining process. You'd really need to re-engineer them and buying a linear transformer and wiring it is more "engineering" than many DIY electronics neophytes can handle.....

Follow GER21's link and you'll do fine....