PC Power Supply external wiring diagram needed 3

[scrafts]

I have a HIPRO HP-235NLXAK 235-watt power supply that I would like to remove from an older computer and use on my bench. The supply does not have a diagram on the case indicating which motherboard wires attach to the on-off switch. My goal is to unplug it from the motherboard, put a little switch on the correct wires, and use it on the bench. I have searched all over the internet to find which are the correct wires to use, but to no avail. Does anyone out there in Tek-Tip land either have such a diagram or know where to find one online? Thanks a lot.

 

[edfair]

None of the wires on the M/B connections connect to the on/off switch. The on/off switch connects to the input of the keepalive circuts on the M/B, and the output of the keepalive circuits in turn connect to the power up circuit in the power supply.

If this is a 20 pin ATX the circuit ends up effectively as one of the black wires connecting to pin 14 (green wire).

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[scrafts]

Thanks Ed. The connector does have 20 pins. Are you saying that I can short one of the seven black wires to the green wire to turn on the supply? Thanks for your quick reply.

 

[ANFPS26]

Here's more info:

http://www.thetechboard.com/tutorials/atx.php

Jim

 

[edfair]

I don't normally suggest that people activate the supply without a load of some type. Some supplies in the past have gone unstable with no load and self destructed. Probably won't, but I hate the smell of overheated electrolytics.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[Frank4d]

Thanks Ed. The connector does have 20 pins. Are you saying that I can short one of the seven black wires to the green wire to turn on the supply? Thanks for your quick reply.

Yes. Shorting the green wire to one of the black ones will turn the PSU on.

There are a couple of other things you should know though to make your life more complicated:

Most computer PSUs expect to see a rather hefty load on the 5VDC output. If not loaded adequately... the 5VDC, 12VDC, and -12VDC outputs will all be low. You will need to connect a permanent load (around 5 ohms, or less) to work around this problem. The minimum power rating for a load resistor should be the output voltage squared, divided by the resistor value in ohms. Example for a 5 ohm resistor: 5V squared / 5 ohms = 5 watts minimum. Use a 10 watt or higher resistor which will dissipate heat better than a 5 watt resistor.

The 3.3VDC output (orange wires) has a sense input (brown wire) wich regulates the 3.3VDC output. You will need to connect the brown wire to one of the orange wires, close to the load, in order for the PSU to regulate the 3.3VDC output to be very close to 3.3VDC.

 

[scrafts]

Thank you all very much for your words of wisdom and suggestions.