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Old 18th January 2004, 11:10 AM   #1
Optical is offline Optical  New Zealand
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Default Modifying PC power supplies?

Does anyone have information on how you could modify a pc power supply to change the voltage levels?
I have a few around so if modifying them is possible then they could make good cheap supplies!
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Old 18th January 2004, 11:48 AM   #2
Ryssen is online now Ryssen  Sweden
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Location: Sweden--> Here
Here:http://www.bleedinedge.com/guides/ps...v_mod_pg1.html
And here:http://www.xtremesystems.org/forums/...threadid=16050
its a start
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Old 18th January 2004, 11:53 AM   #3
Immo_G is offline Immo_G  Australia
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I don't know if you get Silicon Chip magazine over there in NZ, but they did an article where they modded an IPEX standard 250 watt psu, and ended up with 13.8 V @ 25 A, which is a lot of power, but i guess for amp you'd want more voltage.
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Old 18th January 2004, 02:22 PM   #4
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well I do know how to get up to 30V on the 12V line...but I'm stumped about getting a negative voltage...anybody care to answer that??
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Old 18th January 2004, 02:52 PM   #5
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Quote:
Originally posted by li_gangyi
well I do know how to get up to 30V on the 12V line...but I'm stumped about getting a negative voltage...anybody care to answer that??

yeah.. by connecting another rectifier diode and filter cap to the same winding, but in reverse..
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Old 19th January 2004, 03:39 AM   #6
Optical is offline Optical  New Zealand
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ok, thats a good start!
whats the max voltage that people have obtained?
i sortta just skim read all those links, i guess i'll find out for myself tonight when i read them properly..
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Old 19th January 2004, 03:44 AM   #7
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you're going to have to rewind the primary and secondary windings on the transformer... I believe.....
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Old 19th January 2004, 03:54 AM   #8
Benjlv is offline Benjlv  United States
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these sypplys are nothing to mess with...the designs i have seen have had large input caps with one large mosfet doing the switching on the primary of the transformer. This means high voltages! can kill you. And if everything is not perfect in these devices the high voltage tends to conduct where you wouldnt think it would and bang!

anywho...Although it is possible. If youre going with a higher voltage you may need to replace the output caps to support that higher voltage. Also if you double the voltage output the current output in theory will be halfed.

The negative 12volt output and negative 5 volt on power supplys tend to be of the low current variety. Often just using a 7912 as a voltage regulator.
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Old 19th January 2004, 09:09 AM   #9
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yupz that's right the current will be halfed...and yes the -12V is provided by a 7912...
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Old 19th January 2004, 10:50 AM   #10
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Quote:
Originally posted by Benjlv
This means high voltages! can kill you. And if everything is not perfect in these devices the high voltage tends to conduct where you wouldnt think it would and bang!
Agreed. If you don't know the definitions of "basic insulation" and "reinforced insulation" then do yourself a favour and give it a big miss. This NOT meant to sound condescending, but it is not something you should feel your way through. One flash and you're ash.

/Circlotron - plays with audio stuff for fun, but is SMPS professional.
Not immune to electric shock either, BTW.
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