Solved

Bad Power Supply?  PC doesn't boot

Posted on 1998-07-28
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Last Modified: 2010-04-26
My PC is fubar.  When I turn it on I can hear the drive spin up and the PS fan come on.  The normal boot sequence takes about 90 seconds.  The drive clicks for about 10 seconds and then the boot stops.  The monitor does not show anything.  I assume that it is not a HDD problem or I would get the FDD error from the bios, and it can't be a monitor probelm or esle it would complete the boot sequence.  All I can think of is that there is a problem with the motherboard or with the power to the board.  I don't know how to test the PS and see if it is working properly.  The fan and peripherals are powered up but since the motherboard has quite a few more connections I assume that whatever part of the PS supplies the board may be faulted while the rest of it may be operating.  Please tell me how to test the PS output to the Mother Board.  I have a voltmeter but don't know what leads to check and wether to check them to ground (the frame) or to another lead.  
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Question by:ltusnr
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24 Comments
 
LVL 9

Expert Comment

by:rmarotta
ID: 1121757
itusnr,
Here's a link for the poer plug pinouts:

http://name1.cyberzone.net/~donath/pcpspins.htm 

Let me know if you need more.
Regards,
Ralph

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Author Comment

by:ltusnr
ID: 1121758
Ralph, the link you gave me is a good place to start, but I was hoping for a more detailed troubleshooting proceedure.  

Thanks, Jay
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LVL 9

Expert Comment

by:rmarotta
ID: 1121759
Try this:
Remove all adapter cards from the motherboard except video and minimum RAM.
Unplug drive data cables and power supply connectors. (HDD, FDD, CDROM, printer, etc.)
Start computer with monitor & keyboard connected.
Anything on screen?
Keyboard LEDs flash?
Ralph


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LVL 2

Expert Comment

by:harley47
ID: 1121760
What kind of Motherboard is it?  What size power supply (250w 300w)?  
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LVL 4

Expert Comment

by:swwelsh
ID: 1121761
I'm not sure this is your problem, but here's how to test your power supply. Set your multimeter to DCvolts at the next setting above 12v. Plug in the power cord and turn on the power supply switch. CAREFULLY insert the black multimeter probe into the P8 plug on one of the black wires. Put the red multimeter probe into one of the red wires on the P8. You should get +5V. Next put the red probe into the yellow wire. This should give +12v. Next the blue one, should get -12v. On P9 plug, do the same - black probe to black wire. Red probe to the white wire, should get -5v. Do the red wires on P9, they should read  +5v. If you have the newer type power connectors, it should be similar but I haven't tested one so I am not sure. Values within 10 percent or so are ok. In any event, I would be skeptical that this is your problem. In my experience, power supplies go bad rather suddenly. Try the things Ralph said, he didn't get a billion points for nothing.
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LVL 2

Expert Comment

by:SirCaleb
ID: 1121762
rmarotta's suggestion is where I would start....it's the only way you can successfully trouble-shoot your system.
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LVL 1

Expert Comment

by:strowger
ID: 1121763
You can check to see if it is a HDD or FDD problem by disconnecting them(power and data), you'll at least get the memory count, post errors etc.. on your screen.
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Author Comment

by:ltusnr
ID: 1121764
Ok guys, thanks for the answers.  Now for another poser.  In order to see the other answers I had to grade Ralph's original answer.  Now that I have seen all of them I'd like to award some points but I can't seem to figure out how.  Seems like once I graded the original answer the question has been "answered" and the points awarded.  Any suggestions?

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LVL 5

Expert Comment

by:theh95
ID: 1121765
Do you have voltage meter, if you do you can test the power supply. set your voltage meter to DC and the turn on your power supply.  the black wires always ground (-).  you put your (+) lead to the red or yellow wires.  Then you should get the 5 volt and 12 volt read out from your meter.  5 Volt are for most Digital signals and power up the chips, and 12 volt are for the step motors for your drives.  If you got the read out from the meter, you have no problem for your power supply.  If you don't have the meter to test, you can get one from Radio Shack. They cost around $7.00 to $100.00.  The $7.00 one could work for the PC.

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LVL 9

Expert Comment

by:rmarotta
ID: 1121766
>  "In order to see the other answers I had to grade Ralph's original answer."

You haven't graded my answer yet, you rejected it!
You have no grading options right now because I'm submitting a comment.... not a proposed answer.

I'll post another answer when you want me to.... IF I have solved your problem.
 
Any time the answer that has been proposed has not solved the problem to your satisfaction, simply select "Reopen the question to another expert" from your list of options. (You've already done that)  You do not have to accept an answer until your problem is solved.

All you need to do is select a letter to grade an answer when you're satisfied with it.  That will award the points to the expert whose proposed answer is currently pending.

Now, where do you stand, regarding the dead computer problem?

Ralph

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Expert Comment

by:donagustin
ID: 1121767
If your computer actually powers up the peripherals, then the board itself is getting power that it needs.  What it sounds like to me, is that your video card is not working.  Try and drop in another video card, and see if the issue goes away.

Don
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LVL 9

Expert Comment

by:rmarotta
ID: 1121768
ltusnr,
You now have an answer proposed by donagustin.  If it doesn't solve your problem, just reopen the question.
You can reopen the question as many times as it takes, until you are satisfied with an answer, and want to grade it.
Ralph

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Author Comment

by:ltusnr
ID: 1121769
Donagustin, Tried it didn't work.  Ralph, I took your suggestions and stripped out all the components including the drives.  I connected just the keyboard and monitor card.  I get the leds on the keyboard to flash but still nothing further.  Checked all the chips to make sure they were seated properly and checked all the connections.  Everything seems to be fine. And thanks for the info on Q&A
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LVL 12

Expert Comment

by:Otta
ID: 1121770
> I stripped out all the components including the drives.
> I connected just the keyboard and monitor card.
> I get the LEDs on the keyboard to flash but still nothing further.

What more *COULD* happen?
You removed the drives,
so it couldn't even *TRY* to boot.
Re-add a floppy-drive, and try again.
If successful, re-add the hard-drive, and try again.
0
 
LVL 1

Expert Comment

by:strowger
ID: 1121771
No, you would at least get the memory count and controller errors on your screen with no FDD or HDD hooked up.. no need to be *SARCASTIC* and put everything in *CAPS* with *ASTERISKS* around it.. give the guy a break he's asking for your help...
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LVL 12

Expert Comment

by:Otta
ID: 1121772
How does the following help the guy solve his problem?

> no need to be *SARCASTIC* and put everything in *CAPS*
> with *ASTERISKS* around it.. give the guy a break

> he's asking for your help...

To quote the great Homer:  DOUGH!
0
 
LVL 1

Expert Comment

by:strowger
ID: 1121773
I refuse to enter a battle of wits with an unarmed person.. now back to the subject at hand..  

I would say that you more than likely have a bad video card (as donagustin mentioned above) or your supply is gone... most good computer shops have the equipment to test your supply and might have a video card or two laying around to test your machine... the other possibility is that something on your board has gone( bios mebbe)....
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Author Comment

by:ltusnr
ID: 1121774
I tried swapping the video card no dice.  I am not getting the memory count or any beeps from the bios.  Tonight I will try the monitor and take a voltmeter to the power supply.  I'll write back what I find.  I appreciate all of your advice but my problem isn't solved yet
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Author Comment

by:ltusnr
ID: 1121775
Saw something nosty about a CIH virus today that wipes out a flash programable BIOS.....Supposed to trigger ont he 26th....same day my computer failed...hoping and praying that it's just an ugly coincidence.
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Expert Comment

by:johnsonm
ID: 1121776
It does sound as though your bios is faulty, I think it is the virus.
0
 

Author Comment

by:ltusnr
ID: 1121777
OK....irritating as it may be, last night I took the whole thing apart down to the jumper settings on the Main Board and reassebled it piece by piece, testing as I went, and guess what?  The Darn thing is working fine.  WTF???  Anyway, thanks to all of you who assisted in this question.  Ralph, since your second comment was the proceedure I used please post another answer so I can award points.  Thanks again to all of you.  Jay
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LVL 9

Accepted Solution

by:
rmarotta earned 150 total points
ID: 1121778
Glad you got it going, Jay.
Regards,
Ralph

0
 

Author Comment

by:ltusnr
ID: 1121779
Thanks Ralph, now if I only knew what it was that I did to fix it......

Jay
0
 
LVL 9

Expert Comment

by:rmarotta
ID: 1121780
Jay, here's one possibility:
I have seen bent pins in the monitor cord's plug cause the same type of problem.
Simple re-connection inserted the pins far enough into the video card connector to make contact.
Look closely.
Ralph

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