Power Supply Test Button

[bgavin]

I came across a PSU with a test button. The button turns on the supply as long as the button is pushed. PSU is a Newton NPS-160CB-1 160 watts, standard ATX-12.

I don't like the PSU, but do like the test button. I wonder if there is a good use for wiring up a good PSU for the service bench with a switch. I get a number of boards that will not turn on, and think about this feature to force them to power up.

Thoughts?

[Krankshaft]

Re: Power Supply Test Button

Sounds like a good idea the test switch just grounds out the green wire on the ATX connector to turn the PSU on.

The only problem that you may have integrating this into other PSUs is some PSUs need a load to start up.

In other words even if you jumper the green wire to ground the PSU won't start up.

The only solution for this is to either plug in a dummy load like an old hard drive to get the PSU to start.

Or to wire up a 10 Watt 10 Ohm ceramic wire wound resistor from the 5 volt rail to ground.

This will cause the resistor to get really hot however so in order to dissipate the heat you would need to apply thermal compound on to the back of it and zip tie it to the inside of the PSU case so the metal case will dissipate the heat.

Here is a page on designing a bench supply from a computer PSU scroll down to the picture of the ceramic resistor to see how it has to be mounted so it won't burn itself up.

http://www.tc.umn.edu/~beck0778/powersupply.html

As long as you install a switch that grounds out the green wire and install the ceramic load resistor you will be all set with a working switchable test supply.

[bgavin]

Re: Power Supply Test Button

My thinking is more for a bench PSU that is known good, that I can use to force on the board power. I have several Intel boards that are dead, and I'm curious about forcing on the supply to see if the board is dead only in the power-on circuit, or if the whole board is dead.

[gdement]

Re: Power Supply Test Button

I had a PSU set up like that once, I just soldered some extra wires branching off from the green/black wires, and tied them together if I wanted to force something on.
Unfortunately, I don't remember it revealing anything that worked. Occasionally you could get lucky though.
I did have 1 board that worked when forced on, but I already knew about it and had addressed it by soldering the pins on the back of the board. I used it occasionally to test ram, and about 6 months later it died - won't POST anymore.

[PCBONEZ]

Re: Power Supply Test Button

If it's plugged into a motherboard you already have the load to start up the PSU.
All you need is a switch between the green wire and ground.

That said.
PSU's don't kick on because there is something wrong on the board.
You are more likely to damage repairable boards than to get broken ones to boot.

.

[bgavin]

Re: Power Supply Test Button

As of this writing, I don't know-how to shoot power-on bugs on system boards. If they remain dead after recapping, they stay dead...

If I can find tips, tutorials, etc, to self-educate myself on power bugs, I will gladly do so.