17Amp/13.5V Power Supply Conversion

[JRuggiero]

Has anyone tried the computer power supply conversion from the article in Everyday Practical Electronics, July 2006? It converts a typical XT/AT power supply by rewinding the transformer and adjusting the output voltage. In so doing, you lose the 5 volt output, but that's not something that we use, when we want to convert a CPS for battery charger operation.

With 17 amps available (more if you convert a heftier PS), you can run two chargers, at least, and even run some small motors.

Jim R

[coro]

ATX 12V v2.? specification says that psu has two 12V outputs, each around 15A max, so it could be better for two separate chargers.
I dont know the modification, but rewinding trafo is not what I would do.
I have modified some old pc power supplies, by disconnection of whole +5V parts(includng capacitors), creating +5V by voltage dividor from required +12V (the simplest universal suggestion I know). +12V is rock solid then, up to its nominal +12V load.

[Fluke63]

I've searched the web for it, but the only option is to buy the back issue. Is it anywhere to be found? That would match or beat my UPS conversion.

[Chippie]

Has anyone tried the computer power supply conversion from the article in Everyday Practical Electronics, July 2006? It converts a typical XT/AT power supply by rewinding the transformer and adjusting the output voltage.
Jim R

I did a conversion a few years back, but without rewinding the transfo....

Basically I removed all the assoc. stuff with the other rails and modified the feedback loop to monitor the 12v rail adjusted to 13.8v.
I also changed the diodes to those with a higher piv rating....why ?
because the piv of the existing ones was too low, I found this out when I started to load the supply up...they didnt last long and the fireworks also took out the switching transistors....

If you think about how the psu works, the greater the load, the more energy is transferred from the pri to the secondary side....power = volts times amps...hence the demise.

[m2energysolution]

Give this a try... Cheap 30A power suppy.

http://www.rcgroups.com/forums/showthread.php?t=514011

Dave

[JRuggiero]

I was curious about the EPE project, because I've gotten several computer switching supplies for $2 U.S. from thrift stores. Since I'd do the conversion for fun, and if it works for me without too many hassles, and if it can pump out even more current than the EPE project's 17 amps (depending on the total power rating of the original supply) it beats the $40 item from All Electronics. For fun. Otherwise, the All Electronics item is really a great bargain. I've bought stuff from All Electronics several times, so it sounds like a fine deal for $40. But not so much hacking fun.

Jim R

[spatial]

I did a similar mod to what Chippie describes and had a similar result. The supply worked fine for a couple of weeks then fried the output transistors. I wouldn't bother going thru the process again to be honest as it was pretty time consuming for a relative newbie to power supplies.

There are a number of sources for similar sounding mods available for d/l on the net:

http://www.siliconchip.com.au/cms/A_30705/article.html

http://www.qrp4u.de/docs/en/powersupply/

http://www.qsl.net/vk4ba/projects/ps.pdf

The last item is an excellent resource.

cheers
Paul

[JRuggiero]

spatial,

The siliconchip.com article is the same as EPE's.

Jim R