New build won't turn on, makes a zap sound; using a multimeter?

By lazycritic
Nov 19, 2010
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  1. [Solved] New build won't turn on, makes a zap sound; using a multimeter?

    Hi, I am building my first computer - it actually started out an upgrade of an old Compaq, but I had to get a new motherboard (got the ASUS M4A785TD-M EVO AM3 AMD 785G HDMI Micro ATX AMD Motherboard) when I found the new CPU (Phenom II) was not compatible. Basically the problem that I have is similar to what is described in [removed cause I'm a noob] ("New PC Build - PSU makes noise similar to a short 'zap'"). However, I'm not sure the zap sound is coming from the PSU. I have a 600W CoolMax PSU. Like the user in that thread (maXimus4444), I only get a zap once. The motherboard's LED light comes on when I plug in the computer, but when I press the power button there's just the zap and no other signs of power whatsoever.

    I have an old case, motherboard, and CPU that I can test some of the components on, and when I switch these components (PSU, hard-drive, dvd-drive, video card) back to the old motherboard and CPU, the computer boots up OK with no problems that I can see. I cannot test my new CPU on the old motherboard as it can't handle a Phenom II. I also can't test my old CPU on the new motherboard as it doesn't fit the AM3 socket.

    In that other thread, the person eventually said he resolved the problem and this is what he said caused the problem:
    I think he meant to say incorrectly. But I don't really know what that means. Does he mean like the power switch? I've looked at that again and again and it seems OK.

    Couple other things: I found out that my CPU had some bent pins and I bent them back. I haven't noticed any electrostatic discharge but I haven't been taking as much precaution as I probably should. I have about two weeks left to return the items.

    Also, I'd like to learn how to use a multimeter to diagnose problems with a computer. I read [removed cause I'm a noob] at Tom's Hardware ("Do I have a dead motherboard? No beep, no BIOS screen.") and there was a user there (westom) who swore by multimeters for diagnosing problems, but it's not really clear how people use these. I saw [removed cause I'm a noob] at Hardware Heaven ("testing your psu with a multimeter"), but I'm pretty sure I know what my PSU will be saying: no power.
  2. Leeky

    Leeky TS Evangelist Posts: 3,797   +116

    First, could you confirm the following please:

    1. You have tried switching the power switch pins around? In case its on incorrectly, and I will assume you've connected them as per the instructions in the motherboards manual.
    2. You have connected the 12v ATX (4pin) power connector to the motherboard
    3. You have connected the big (20/4) pin power connector to the motherboard
    4. You have connected the CPU cooler fan lead to the CPU FAN connector on the motherboard.

    It's possible you have recieved a dead PSU, but I would say its more likely the power header is incorrectly fitted.
  3. lazycritic

    lazycritic TS Rookie Topic Starter

    What do you mean by switching the power switch pins around? I don't understand the terminology? I think I have it in the correct place based on my reading of the motherboard manual. I also read online that the reset switch will do the same thing so I tried putting the reset switch on the power switch pins and pressing the reset button - same thing happens. It is correct that neither of the two pins are ground for power, right?? I haven't tried turning them around- I have the wording on the connectors facing the bottom of the case.

    The power connectors are connected to the motherboard, yep.

    It's not possible that I have a dead PSU, as my PSU works just fine when I use it for my old motherboard and CPU.

    What is a power "header"?
  4. Leeky

    Leeky TS Evangelist Posts: 3,797   +116

    That rules out the faulty PSU idea then.

    On the motherboard, you have the headers for the PWR switch, reset switch, HDD LED and PWR LED. The manual will explain where they need to go - Sometimes all the problem is, is the PWR switch is the wrong way around.

    Its also possible if the pins were damaged on the CPU that its damaged, but I'm pretty sure it would still power up, hence my first thought being the PWR switch being incorrectly fitted.

    As far as I am aware, 1 pin is ground, and the other is a positive feed.

    I would remove all the connectors from the header, and then refit just the PWR switch. If that doesnt work, turn it 180 degrees and refit it and try again. Once it powers up, you can fit the other connectors to the header.

    As far as memory serves me, the white wires are ground, and colour wires are positive feed.
  5. lazycritic

    lazycritic TS Rookie Topic Starter

    I tried your suggestion. It didn't work - I'm getting the same sound either way I have the power switch connector plugged into the pins. After I get 5 posts I may post a picture to make sure I have it right, but I'm pretty sure it is (there's one space between the reset pins and the power pins whereas the speaker pins are all together). Thanks a lot for your suggestion though.
  6. Leeky

    Leeky TS Evangelist Posts: 3,797   +116

    Below is the header diagram:


    You need to be concerned with PWRSW. Ensure the white wire is connected to ground as shown in the diagram, and the coloured to PWR.

    Is your connector fitted as shown in the diagram?
  7. lazycritic

    lazycritic TS Rookie Topic Starter

    I think so.. I'm about ready to return the motherboard and CPU. Or maybe just the motherboard? Hmm.
  8. lazycritic

    lazycritic TS Rookie Topic Starter

  9. Leeky

    Leeky TS Evangelist Posts: 3,797   +116

    Looks good to me, I would RMA the motherboard.
  10. lazycritic

    lazycritic TS Rookie Topic Starter

    I'm actually going to have an A+ certified guy look at it first.
  11. lazycritic

    lazycritic TS Rookie Topic Starter

    So the A+ certified guy found the problem. Whenever you hear that zapping sound there's some sort of power issue, I imagine. He said I had my power supply plugged into some printer (LPT) power thing, and that a few years ago he would've expected it to fry the motherboard. But everything's fine and I'm running my new (much faster!) machine right now. Yay! I haven't bothered to open it up to see what he's talking about because I'm just too burnt on opening up my case, but maybe I will look for it someday.

    I gave the guy a bunch of old parts and he charged me $50. Good thing I didn't send the motherboard and CPU back, as that would have just been a big hassle for everyone.

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