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View Full Version : MB gets power but nothing turns on.......



mateor6
04-24-2005, 11:40 PM
i have a amd 3000+ 400mhz FSB on a asus board (not sure of model, ill post that when i find it out).

well here is the story....i was playing counter strike with absolutley NO problems......when out of nowhere the entire computer shut off abruptly and would not power back on........there is however a green light on the MB that lights up. when i press the power button absolutly NOTHING happens. :mad:

is my power supply fried? or is it more serious? if you guys need more info on my stuff let me know....im not at home and i cant remember the part name or numbers.......

thanks for all your help in advance....

Whyzman
04-25-2005, 12:27 AM
absolutly NOTHING happens.No fans spinning up...nada?

If nothing, you might want to see if you can swap out the power supply with a known good one...

Welcome to the PC Guide Forums!

mateor6
04-25-2005, 01:32 AM
yes you are correct......NOTHING!!!!

its like im not even doing anything........

thank you for the kind welcome and i really think the members of this forum are great and can really help people out....i hope they can help me out the same!!!

ill try to swap out the power supply tomorrow...but why is that green led on if the power supply is toast......???

please help i spent 1300 on a gaming rig that i havent used in months.....had a backup comp and now that one starts up with an error beep of one long and 2 short........i think that means a video failure......replacing the video card should solve that correct??

Sylvander
04-25-2005, 04:10 AM
Download a copy of my diagnostic flowcharts from here
www.erniek.eclipse.co.uk/downloads/sylvanderdiags.zip
and print them to leaf through.
Begin on the STARTUP chart.

TESTING ATX POWER VOLTAGES
See this
http://www.ochardware.com/articles/psuvolt/psuvolt2.html

Black = ground
Red = +5 volts
White = -5 volts
Yellow = +12 volts
Blue = -12 volts
Orange = +3.3 volts (?)
Green = power on

Turn the power on. The fans should at least come on so that you know you have power.

Turn on the voltmeter and set it to measure DC voltage. Start with an IDE power connector that is not used. Place the black lead of the voltmeter in the hole of the connector that has a black wire (ground). Connect the red lead of the voltmeter first to the yellow hole and then to the red hole. The voltmeter should read +12v and +5v respectively.

The other voltages may usually be measured at the motherboard power connector by simply sliding the red multimeter test probe down the hole where each colour wire goes (with the black probe connected to any black wire as before). Really you only need to check the orange wire for 3.3 volts at this connector. If +12, +5, and +3.3 volts are all okay, then your power supply is probably fine.

Unfortunately, a low voltage measured in this way may mean a bad PSU or that some other component (motherboard, etc.) has a short and is pulling the voltage down. Therefore, the main value of measuring voltages is to eliminate the PSU as a source of the problem (if it has normal voltages).

I'm inclined to think that the LED indicates your PC is not "dead" and that you have NO POST, so you need to try a "Bare-Bones Boot".

Yesterday I connected a USB plug the wrong way round and my PC shut down [dead] and wouldn't come to life until I reversed the orientation!
You didn't do that did you?

Whyzman
04-25-2005, 10:00 AM
As Sylvander points out, a power supply essentially has 4 "pumps" inside producing differing voltages. What is lighting the green LED is more than likely just one of the voltage pumps or what we call rails...

Unfortunately, troubleshooting is quite often a process of elimination since most of us don't have the necessary testing equipment. We look for certain symptoms but the real problem can oft times be hidden because there are other other components that can produce similar symptoms when they fail.

What I was hoping for was that you might have another computer with a "swappable" power supply for testing, rather than running out and purchasing a new one to do so. Being able to swap a component out is just a quick way through the process of elimination...

As Sylvander aptly points out, there are other possibilities...

mateor6
04-25-2005, 01:50 PM
Download a copy of my diagnostic flowcharts from here
www.erniek.eclipse.co.uk/downloads/sylvanderdiags.zip
and print them to leaf through.
Begin on the STARTUP chart.

TESTING ATX POWER VOLTAGES
See this
http://www.ochardware.com/articles/psuvolt/psuvolt2.html

Black = ground
Red = +5 volts
White = -5 volts
Yellow = +12 volts
Blue = -12 volts
Orange = +3.3 volts (?)
Green = power on

Turn the power on. The fans should at least come on so that you know you have power.

Turn on the voltmeter and set it to measure DC voltage. Start with an IDE power connector that is not used. Place the black lead of the voltmeter in the hole of the connector that has a black wire (ground). Connect the red lead of the voltmeter first to the yellow hole and then to the red hole. The voltmeter should read +12v and +5v respectively.

The other voltages may usually be measured at the motherboard power connector by simply sliding the red multimeter test probe down the hole where each colour wire goes (with the black probe connected to any black wire as before). Really you only need to check the orange wire for 3.3 volts at this connector. If +12, +5, and +3.3 volts are all okay, then your power supply is probably fine.

Unfortunately, a low voltage measured in this way may mean a bad PSU or that some other component (motherboard, etc.) has a short and is pulling the voltage down. Therefore, the main value of measuring voltages is to eliminate the PSU as a source of the problem (if it has normal voltages).

I'm inclined to think that the LED indicates your PC is not "dead" and that you have NO POST, so you need to try a "Bare-Bones Boot".

Yesterday I connected a USB plug the wrong way round and my PC shut down [dead] and wouldn't come to life until I reversed the orientation!
You didn't do that did you?

no i didnt connect anything abnormally.....i was playing a game and out of nowhere it shut off. didnt go into shut down mode....it just switched off immediately.
i dont have a voltmeter so i think the best approach at this is process of elimination.....the power supply came with the case and the case and the power supply only cost me 30 bucks.....so maybe i just bought a POS power supply? i hope thats the case. i have a spare power supply but it wont power my video card too. i think ill just go buy one and take it back if it doest fix the problem here.......i hate to do that but i think i may have to.

thanks for you help so far.......that diagram is great.

As Sylvander points out, a power supply essentially has 4 "pumps" inside producing differing voltages. What is lighting the green LED is more than likely just one of the voltage pumps or what we call rails...

Unfortunately, troubleshooting is quite often a process of elimination since most of us don't have the necessary testing equipment. We look for certain symptoms but the real problem can oft times be hidden because there are other other components that can produce similar symptoms when they fail.

What I was hoping for was that you might have another computer with a "swappable" power supply for testing, rather than running out and purchasing a new one to do so. Being able to swap a component out is just a quick way through the process of elimination...

As Sylvander aptly points out, there are other possibilities...

yea i think this may work best for me considering i have no testing materials on hand.



If the power supply works......what else would it be? the mobo?

mateor6
04-25-2005, 02:18 PM
http://usa.asus.com/products/mb/socketa/a7n8x-e-d/overview.htm?m=a7n8x

thats my mobo im running. i also have a 10,000 rpm 37GB hard drive. ati 9800 pro video card. that might help out a lil bit.

Sylvander
04-25-2005, 04:46 PM
You're trying to find the culprit responsible for this problem [failure to POST].
A bare-bones boot will reduce the number of connected items to a minimum, and therefore reduce the number of possible culprits.
If the PC POST's after you remove all unnecessary items, then you know one of those is responsible.
If it still fails to POST, then you know one of the few remaining connected items is responsible.

mateor6
04-25-2005, 06:08 PM
sweeet....ill be taking it all out except for the HD and MOBO later today and see what she does.......i have an extra power supply that i can toss in to see if it works but it wont be able to run the video card too......

and i dont want to try to do the stuff explained in the otehr post. seems to dangerous for me to do on a 1000+ system. im a newb at this stuff.

Paleo Pete
04-26-2005, 12:31 AM
OK, I think you said you had a second computer that you're using now to post this right? So take the power supply out of the problem machine and plug it into the one you're using now. Unplug only the main power cable that hooks to the motherboard, plug the test power supply in. No need to remove anything but that one connector, you just want to see a picture. If it powers up and tries to boot, your power supply is not toasted. If you get the same results as in the other machine, then it's time for a bit of surgery but there's no need to overcomplicate matters by removing everything in your computer.

That's not a definitive test, if it does power up you'll want to hook that power supply up fully to make sure it still works while under a load, instead of just enough for video. That's not that hard either and does not require complete disassembly, and only takes a few minutes to swap out.

Lay it on its side and put the test power supply on the upper corner where the existing (installed) power supply is, make sure it won't fall off easily. I like to put a mouse pad under them so they can't slip off and into the machine easily. If the cables are long enough you can hook up everything that way but be careful and be sure to put something under it so it won't slide easily.

For the other machine with the BIOS beep error code, reseat the video card a few times and try it, chances are the video card is not bad, just getting bad contact. (RAM can do the same thing but will pprobably produce a different error code, I would reseat both if I were going to be inside the case anyway.) Reseating it should clean up the contacts so it can run. That's quite common when a computer is stored or transported. You can use that machine to test the other power supply once you get the video sorted out, but get the video right first so you don't have multiple problems to try and figure out. Be sure you unplug it from the wall socket before removing the video card, some boards still have low lever current running even when shut down, I've fried 2 AGP video cards by forgetting to unplug the machines while reseating video cards.

mateor6
04-27-2005, 05:37 PM
sounds good...ill be getting to this in the next day or two...ive been super busy lately......

ill post back up if it fixes the problems or not.....

and yes im using my laptop from home to access the internet.....
though, im at work now