Power Supply Problems?

[Mike T]

Hope you Guys can help. When i start my computer the processor fan and graphics fans start but all i get on the display is a flashing led. Iv'e tried a different graphics card with the same results. on the very odd occasion the system boots up normally but not often. Is this a problem with the power supply or anyone got any ideas??
athlon 800 , voodoo 5 graphics , 512 ram

[yawningdog]

Are you getting any beeps?

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Give a man a fish, and you feed him for a day. Teach him to use the net, and he wont bother you for weeks.

[Mike T]

No beeps and no click sound as the graphics kick in.
Does the atx power supply have to kick in any extra voltage to start the display signal to the monitor as the noises from the comp seem the same up to the point when the graphics are due to appear?
Do you know of any way to check out an atx power supply without being connected to a m/b?

[YODA74]

If you have used a multimeter before you can check it. if not get a cheap one at hardware store and check here to show how to use it properly.


http://www.users.dircon.co.uk/~doctron/meter.htm

[bassman]

Hi Mike,
Funny, it seems when it rains it pours. We have had a lot of questions on no display lately.
If you mean by saying "flashing LED" that all you see on the screen is a small rectangle curser blinking, then I think you need to test your RAM.
Do you see anything on the dislay during startup?

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If I tell you to think for yourself, then you're not doing it.
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This is not directed at those asking questions in order to gain knowledge. That shows you are thinking.

[Mike T]

Thanks for the replies guys, now to answer your questions.
The flashing led is the power led of the monitor. When the monitor is powered up on its own, the led is steady. If i then connect to the graphics output of the computer with the computer plugged into the mains but not switched on, but still earthed, the led of the monitor starts to flash after about two seconds. I've tried another graphics card with the same results. I should add that the original card is an AGP but the second one i tried was PCI.
I can't see anything on the screen, it doesn't seem to be able to get to the stage of the boot sequence where the graphics come on.
Just as background, as it might be important, the original power supply in the computer failed and i have put in another that i beleived was ok, but i'm now wondering whether
a)the original failure damaged anything else, or
b)my replacement is faulty
Any further ideas guys?

[yawningdog]

I'm guessing you've got a monitor problem. Swap with a known good one and see if it works.

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Give a man a fish, and you feed him for a day. Teach him to use the net, and he wont bother you for weeks.

[hacker]

Have you tried a different monitor or another cable?

Have to rule out everything.

Oops, yawningdog bet me to it.

Good Luck!



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I was called "hacker" before there was a HeathKit.

[Mike T]

Just to update those interested:
I have taken out all peripherals from the system only leaving m/b, processor, memory and graphics but still have the no boot problem but now think that i have isolated the problem. A friend has a diagnostic card that plugs into an isa slot a gives you an indication of the point at which the boot up sequence has stopped. This indicated that the processor was not running at all so obviously no boot! We swapped this suspect chip over into a known working system and -- no boot. We put the good chip into the suspect system and it booted. So obviously the processor looks to be faulty but it wasn't that simple. When we removed the heat sink from this suspect chip, the whole face was smeared with what i think was conductive compound. After this was cleaned off the processor would boot, but only once!!! We tried this a number of times with the same result, Give it a good clean with isopropenol and it would boot once but despite numerous attempts, not again until it was recleaned.
I am obviously going to replace the chip but has anyone any idea why this is happening???

[mjc]

Way too much thermal paste...could be shorting something out...try removing all of it it both off the chip and the heatsink....

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mjc
Links list:Computer Links (http://www.dreamwater.org/tech/mjc/index.htm)

Celts are the men that heaven made mad, For all their battles are merry and their songs are all sad.

[Mike T]

I have cleaned the processor and heat sink thoroughly ( many times with various cleaning substances ) and even used compesssed air to make sure there was no fluid left around the raised components on the chip face. This still results in the processor working first time after each cleaning operation, but not again. Could there be a capacitor on the chip that needs discharging, and this only occurs when the chip is removed, cleaned and replaced? As i said, the processor will be replaced, but i would like to know what the problem was.

[This message has been edited by Mike T (edited 09-24-2001).]

[bassman]

Im starting to think you have a connection problem. When you remove and replace the chip, you make a good contact and all is well??? But when you restart on this same installation you loose that contact and POOF no boot.
Is there any carrosion or deposits on the legs of the chip or in the socket?

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If I tell you to think for yourself, then you're not doing it.
.
.
This is not directed at those asking questions in order to gain knowledge. That shows you are thinking.

[Mike T]

i can't see any corrosion on the chip legs or in the socket. What makes me think it is a chip problem is that this chip won't work in any other motherboard and known good chips will boot repeatedly in the suspect m/b, indicating that the m/b is ok. Also, if only removed and replaced the chip will still not boot, it seems that the handling and cleaning process has some unknown effect.

[Mike T]

Just thought i'd update you guys just as info.
The offending comp' went back to the original seller who was unable/unwilling to repair so i got it back again.
As i'd got nothing to loose, i scubbed, and i mean SCRUBBED!! the back of the processor with a copper wire brush and petrol!, washed it in petrol and then blew off the surplus with a compressed air line and replaced into the m/b. Guess what? IT WORKED!!!!!!!!!!!!!! and has continued to work ok.
I think mjc was right when he suspected an electrical short due to too much heat compound.
Just goes to show - never give up!!
Thanks for all the suggestions.

[mjc]

Well, I guess that is one way to clean it....but usually something a little less drastic will clean them up. http://www.PCGuide.com/ubb/biggrin.gif

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mjc
Links list:Computer Links (http://www.dreamwater.org/tech/mjc/index.htm)

Celts are the men that heaven made mad, For all their battles are merry and their songs are all sad.