ATX Power Supply Shutdown

[can773]

I have a 600W ATX power supply with a 10 ohm resistor on the PS-on line.

It works fine when my two Schulze isl-6 and Triton are hooked to it, however when I hook an Apache 2500 or my Dymond Super Turbo to it the supply shuts down. Cylcing the switch or removing the power cord and reattaching gets it going again.

I get 12.05V no load on the output.

How can I get this supply working properly with the Apache chargers?

TIA

Chad Northeast
www.f3acanada.org

[chrisgood]

I am guessing you have the resistor across one of the 5v lines. I have a similar setup on my four power supplies. When I turn on the power supply and then plug in a charger on the 12v line, it turns off. When I have the charger already plugged in when the power supply is turned on, everything works fine. These power supplies must also sense loads on the 12v lines and turn off at startup if no load is there. I have not modified any of my power supplies - I do the same thing you do; I turn it off and then on again and the load at bootup must be enough to trigger the supply to stay on. I have not done this, but maybe a resisitor across the 12v line would keep it on. The only problem is that you will lose some of you total wattage to heat generated by the 10ohm resistor on that line.

The charger that requires this must not have much of a load at startup and is not enough to trigger the power supply to stay on.

Chris

[jkmadsci]

you should be hooking up the 10 ohm resistor to the 5 volt line, NOT the ps on line!!!!!

[chrisgood]

Good catch Jkmadsci. I had completely missed that when I read the post the first time. The 10 ohm resistor goes from a 5v line to ground. Make sure to give some type of heatsink to the heat generated by the resistor.

Chris

[Andrew0820]

jkmadsci is correct that your load should be on the 5v rail. The PS_ON is run to ground generally thru a switch. One other option you may want to try is increasing the load on the 5v rail by replacing the 10 ohm resistor with two 1 ohm 10 watt resistors wired in series. Don't use a single 2 ohm resistor as a replacement for the two 1 ohm resistors since you need to split the power consumed in the circuit. They will get hot and should be attached to either the case or heatsink. The purpose is to boost the output voltage on the 12v rail and reduce the current demands placed on that rail by external devices.

Keep in mind that these PS's are being used for a purpose outside of their design parameters. Some of the chargers produce a high current sink when attached and appear to the overload circuitry as an internal short in a PC, causing a shutdown. Attaching the charger before powering up the supply will sometimes alleviate the shutdown problem.

A 600W PS is a hoss and should carry any charger, even with high mah LiPo's.

[adamg]

Thanks guys, we would have never figured that out without your help. Chad will re-wire the PS soon.

I'm rather surprised it worked as we wired it. We were charging two gel cells at the same time, each at 14.3v and 5.5amps out, so pulling ~180 watts from the PS, without the PS dropping below 12.0v.

[adamg]

Chad re-wired:
red-10ohmResistor-black
green-switch-black

It completely killed the power supply, which now won't show voltage across any lines or power up under any circumstances.

What went wrong? I'm pretty certain it is an ATX power supply, as there is no switch and it has the grey and green lines as expected. It worked almost perfectly before.

[chrisgood]

Make sure it is an ATX. Also, these colors are good 99% of the time. Refer to these articles to identify the supply and for more details.

http://www.marcee.org/Articles/PCPowerSupply.htm

http://web2.murraystate.edu/andy.batts/ps/powersupply.htm

The 10ohm 10 watt resisitor needs to have a good heatsink. You are using a big sandbar resistor, right?


Chris

[jkmadsci]

ps on needs to be grounded to turn on the supply. reground it through a switch!
5volts needs a 10 ohm resistor (sometimes) to help regulate the spikes produced
by the switcher!. hope this helps

[can773]

Hi Chris

Yep we had the sandbar type resistor mounted to the heatsinks in the PS. Its entirely possible that I just shorted something when re-wiring :mad: I didnt think so at the time, but now I am not so sure anymore......

Will get another and give it another try.

So are you guys wiring everything up completely before putting power to the unit?

Chad

[adamg]

I wired mine up as everyone is recommending and it puts 12.05v to the yellow lines with a single 10ohm resistor.

Chad must have shorted something.

Thanks for the help, all.