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Motherboard bad???

Posted on 2003-03-12
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Need some advice. I connected a new power supply to a computer which was not working. The old PSU was only registering .1V when it should have been 5V. Anyway, hooked it up to the motherboard. No response. Not even a beep. No lights. No nothing. Anything I can do to test my mother board out? I know I can buy a diagnostic board but I would rather do some test with my multimeter. Like anyone know how to test the power switch? Any help would be greatly appreciated!

Thanks
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Question by:keakathleen
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Expert Comment

by:kiranghag
ID: 8124752
afik, atx power supply can be tricky to test without load, they require a click button to be conected to the motherboard. i havent figured out any way to test it alone...let some experts comment on this.

but i think u can test it while connected to the motherboard.

does the fan spin when u turn it on currently????
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by:keakathleen
ID: 8124772
No. The fan doesn't spin. I have problems with the battery not staying put. However, when I hold the battery in I still get no response. I have tried switching the red voltage switch from 115 to 230 without any result.
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by:m0nk3y
ID: 8125329
First off, the red voltage switch is useless in most parts of north america, it's purpose is so that if you ever find yourself in a part of the world (ie most of the uk) where the current is 230 instead of the 115 or 120 that we have here you don't need to buy a new psu.

To test out a psu all you have to do is short pin 8 and pin 17 (using standard numbering, starting bottom left going counter-clockwise. The clip should be on the top, also there should be some sort of markings indicating the first pin).. they should be the third from the right on the bottom row and the fourth from the left on the top row.. should be a green wire and a grey wire, atleast that's the standard.. if you get the wiring upside down, both the pins are ground so you don't need to worry about it (lol also an indication if you've got it upside down).

Now the thing is, almost always when a psu "dies" it's just that it can't handle the current being drawn by the system.. so a dead psu (lol like the one i have sitting in a box in my closet) that you short will still turn on, although you can check the voltages/current to see if anythings awry.

That said, there's one of two things that could be wrong. Either the mobo is dead, or the video card is dead.. Especially if it's an AGP card, that's really common (actually happened to me once). Try sticking in a PCI vid card, and just seeing if it boots.. if it does, then you're definately dealing with a AGP issue.. the thing is, a mobo's AGP circutry can be blown and the rest will still work, so you have to find out if the vid card now still works (by trying it out in a different system). By a process of elimination you should be able to figure out what you need to replace.. lol or hopefully RMA.
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Expert Comment

by:ykchick
ID: 8141506
Is this an ATX motherboard or an older motherboard? On an ATX motherboard, just switching the master power switch on the power supply should result in some "action" - fans coming on, network adapters lighting up, etc - even before you use the power switch on the front of the case. However, it if it AT or other style motherboard and power supply, then I'm wondering if it might be something as simple as the wires from the power switch being incorrectly connected to the motherboard?

I am probably over-simplifying this because I'm not sure whether you mean the power switch on the power supply or the power switch on the front of the case when you said you wanted to test it.
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by:keakathleen
ID: 8155351
Thank you all for your advice. I have an 250 Watt ATX power supply (brand new) connected to a fairly new motherboard with an Athlon processor (the Athlon processor has a fan mounted on top plugged into the motherboard. So, I have connected my power supply to the motherboard with the one 20-pin connector. This computer used to work. It has stopped working within the last year. When I turn the switch on the back of the power supply, nothing happens. No fans turn on...nothing. I thought this was normal though because on my other computers nothing starts up until I punch in the power switch on the front.

So, PSU definitely works! How can I test to see if my motherboard is shot or if my peripherals are somehow hanging up my system? (Rewording of the original question above!)
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by:keakathleen
ID: 8155356
BTW, I plugged in an AGP video card that I KNOW works. Still nothing...
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by:kiranghag
ID: 8160703
must be dead supply or fuse inside the supply is blown out.

the red switch is not meant to be a "lets try to see if this works" job...it is meant to be flipped only if u know what u are doing...

try with a new power supply...
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Accepted Solution

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m0nk3y earned 200 total points
ID: 8161200
Ok, well lets first look at all the things that could cause the system not to post (without any error-beeps).

-bad psu
-bad cpu
-bad ram (sometimes.. usually it'll give an error (beep) code atleast)
-bad AGP card
-last but not least bad mobo.

Now we know it's not the psu or videocard by cross-checking, and like i said, the ram would give you an error code, so we can rule that out with a resonable doubt. That leaves CPU and mobo. Now what i'd suggest is to get your hands on a PCI videocard, and try it out in the system. The reason i say this is, the AGP circutry is very fragile and can eazily be fried even though the rest of the system is fine. So try that, and if still nothing it's either your mobo is completely fuX0red or your CPU is gone, in which case your best bet is to take it into your local comp store and tell them that if they'll test your cpu/mobo out you'll buy what's not working :)..

Now the other thing is, and i just wanted to clarify this because you were kinda vague when you said it: for any ATX system you need to use the power on the front of the system to get it going. The reason for this is that ATX was designed so that the motherboard (and therfore any software running on the mobo, ie the OS) could manage the power of the system; in laymans terms, when you tell windows to shut down it turns the power off for you. The thing is, you didn't say that you connected the power button and used that (as well as making sure the psu switch was on).


kiranghag, just because the system doesnt power up at all doesn't mean the psu is dead or it's fuse is blown. If you read keakathleen's 2 previoud posts you find that it is a brand new psu. With ATX systems, the psu is partially controlled by the mobo (refer to previous paragraph).

Also, the red switch isn't meant to be flipped at all, unless you are traveling to a country that has 230v instead of the north-american 120v or 115v.

I suggest you read keakathleen's post again, she is using a new psu already.
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by:keakathleen
ID: 8170661
Thank you very much m0nk3y. I will see if I can get my hands on a PCI video card just to make sure that is not the problem. I appreciate all of your help.
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by:m0nk3y
ID: 8171691
np.. :) that's what ee is for!
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