atx psu problems..

[kiss]

i just purchased a 375w atx power supply from a store down the road. while at the store this little unit was tested, and found to be in perfect order. when i got home i started the usuall business of grouping like wires together, ect. now for some unknown reason 1. my fan hasn't come on at all. temps. are low anyway but..... 2. the 5 volt side is given me issues. when i power on i get a perfect reading of 5.31volts. However when i hook this up to my chlorate cell it seems to shut off. when i use the 3.3v the unit works like a champ. any ideas on this? what am i missing?

[bikemaster]

I am not sure, but if you have some sort of protect on shortcut on the power supply, maybe it just close for protection. If you want to test this, make sure that you electrode don't touch each other and then wire the 5v wire by wire (that will limite the current flow) until it shout down. If it shout down after only one wire.... I have no clue...but try this first. Also you said the the fan was not working. Does it was on the 5v only or even when you use 3v?

[kiss]

hey Bike,

well i just opened the top again to have a look. looking at the fan i see the small red and black leads for it, running to the board. exactly at that point there are 2 other wires, one is the single gray wire and the other one is the same color as the 3volt wires. now i had this same color wire grouped in with my 3 volt bundle. the gray wire is connected to nothing as i thought this was the norm.

i took the single green wire and joined it with one of the blacks as recommend in order to by pass.

[kiss]

forgot to mention the fan hasn't ran at all.

[FrankRizzo]

forgot to mention the fan hasn't ran at all.

 

If the fan isn't running, the supply isn't turning on. As a test, load the 5V rail with the load from a 60W or 100W lightbulb before turning the power on. Most ATX supplies need a draw on the 5V rail before they will turn on. If your electrode spacing is too close, you also may be drawing too much current, causing the power supply to power off.

 

The gray wire should not be connected to anything.

Edited September 18, 2010 by FrankRizzo

[kiss]

ok tried the test with a 40w light and nothing happend. all the while checking with my volt meter, which read 5 volts till ii touched my electrodes . thats when power shuts down.

l'm lost here. everything seems to be fine when i run my cell with the 3.3 volts.

[GaveUpOnTV]

From what I understand (and am able to communicate) it needs (some wires need) some load on it. You have to put some resistors on some 'voltage sensing' wire, there have been a lot of people who have written about it (lab power from computer supply-good cheap way for power for electrolysis, plating, etc.)

 

http://webpages.charter.net/dawill/tmoranwms/Chem_Chlorate.html (good overall, although he doesn't get into the specifics of his power supply)

http://oxidizing.110mb.com/chlorate/powersup.html (although he sticks with transformer type supplies, not the switched mode that modern computer supplies are)

http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply (specifically dealing with switched mode computer power supplies into lab power supplies)

MOT (Microwave Oven Transformer) secondary cut off and rewound for a low voltage chlorate power supply (be careful of microwave oven transformers-they can put enough voltage out to kill you when they aren't rewound

http://vk2zay.net/article/63 I haven't read this yet but seems good

this guy's video is good-he's about expediency and low cost. I like his idea of using car alternator diodes-cheap and high power!

http://yeroc.us/eng/at-atx-bench-supply this guy mentions that the 5 volt rail needs about 250 ma to stay on.

[Verge]

Well um, I recommend trying to actually get an older one were they have the power button built in.So,how do you turn your psu on?Do you use the green to black wire trick or what?

Yea,but anyway it might be easier to get an old 250watt one and just use the 5volt rail.

 

Edit:

I do actually have one that we changed into a variable psu,but dangn;t lost my train of thought come back to it later.

Edited January 15, 2012 by Verge

[mike_au]

Well um, I recommend trying to actually get an older one were they have the power button built in.So,how do you turn your psu on?Do you use the green to black wire trick or what?

 

The ones with the power button attached to the PSU are AT rather than ATX, they have been obsolete for a good 15 years so they might be a bit rare by now.

 

Yes, an ATX PSU is powered on by shorting the green wire to ground.

[djjudas21]

Might be of use http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply