Tesing a PSU with a multimeter???

[ajf3]

Hey all,

I have an Antec TruePower 550 that seems to have died - won't start up the machine at all, but when I replace it with a spare 350w I have here, the machine works fine. Given this, I'm making the assumption that there's a problem with the Antec.

Anyway, I bought it off a guy here & I'm waiting to hear from him about whether or not he has the original purchase receipt since Antec requires it for warranty service (3 year warranty).

I tried the thing where you short the two pins to let it register the ON signal which should allow it to turn on while not connected to a mobo - doesn't work. I can't open it to inspect the inside since theres a voids warranty sticker sealing it closed.

I have a digitial multimeter here, so I wanted to see if there are any further tests I can do while waiting to see if I can get the receipt, so I wanted to see if anyone had a link to a web tutorial on what to test out... Checked google, but didn't come across anything sufficient - anyone have a link?

Thx!

BTW - anyone else have problems with the TruePower 550's?

 

[LiLithTecH]

In order to check the POWER ON signal (orange wire and grnd) it needs to
be under a load (plug-in a old CDROM drive).

Wire Color, Voltage, and Uses

Red +5V, Motherboard, adapter cards, disk drives
White -5V, Logic circuits (rarely used in modern PCs)
Yellow +12V, Disk drive motors, RS-232 serial port, fans, adapter cards
Blue -12V, RS-232 serial port, fans
Orange = Power OK signal
Black = Ground (GND)

Without opening the unit, there really is not much else to test externally.

 

[Ryoga]

I've never known anyone to have problems with an Antec TruePower PSU.

I don't have a tutorial for you, but I have used a multimeter personally before to test a PSU.

First, get a pinout of the voltages of the P1 connector (the thing that attaches to the motherboard). One the disk drive connectors, the blacks are ground, the red is +5V, and the yellow is +12V (IIRC, might have the voltages swapped).

Next, power on the PSU. I've only done this with PSUs I was suspicious of and didn't have a mobo sensor, but they all powered up fine. You can even test voltage while the PSU is connected to the motherboard.

Next set the meter to 20 volts (or whatever voltage you have that's the next higher than 12... it's usually 20).

To test the voltage, you use a method known as back-tapping. Basically, you stick the multimeter probe in the back of the molex connector next to the wire far enough to touch the pins. First, place the black lead in any of the ground pins on the system. It doesn't matter which, they should all have the same voltage. Now just go through and test all the voltages. All of them should have fairly standard voltages (+3.3, ±5, ±12) within a 5% tolerance. The positive voltage lines are the most important; the negatives are rarely used currently so you can use a 10% tolerance on them. Pin 8, usually gray, tends to have some random voltage around 1 to 2 volts, but because this line supples no power (it's a signal line) it's not very relevant what the voltage is.

here is a PDF with a complete description of the ATX 2.1 form factor. The PSU specs begin on page 19, and it includes pinouts for the Main (P1), Aux, +12V P4, and HD/CD/Floppy connectors. It also includes the specified tolerance levels.

(Note: If you have an antistatic wristband, do NOT use it for this test. You do not want to be ground to a powered on system.)

 

[ajf3]

Hey -

Thanks for the detailed instructions! I did have it connected to some drives when I tried to get it to switch on by jumpering those pins, so I guess it is dead. The guy I traded with got back to me & he did have the receipt, so I guess it's back off to Antec it goes!

Thanks!