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computer won't power up


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#1
tybee

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I am in the process of upgrading two computers. One gets new stuff and one gets my old stuff. My problem occurred when I tried to power up the second computer with my old stuff. The fans (cpu, video card, case, and ps) all come on for maybe 1 second and then shut off... that's it. I have to remove and reapply power to repeat the cycle.

I have some experience in building and upgrading computers and some experience in troubleshooting but not diagnosing problems like this. I don't know what parameters or components to check. I have rechecked my install connections several times; removing and reinstalling everything. Nothing looks obvious and I don't know what to check for next.

I sure would appreciate some help. Thank you in advance.
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#2
rshaffer61

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By rebuilding does this mean you put a different MOBO in?
If so you may have accidentally have gotten a standoff in the wrong place under the MOBO.
This would cause a short resulting in the issue you are having.
Try the next steps to check this.

Disconnect everything from the Motherboard except

* keyboard
* mouse
* video output
* 20+4 powercable
* 4/8 pin 12v wire both coming from the powersupply,
* Cpu fan wire
* power and reset button to the case
*case speaker

Now you should have NOTHING connected to the motherboard except what was listed above.

The goal here is just to test the mobo:

If the computer still will not boot up the please remove the motherboard from the computer along with the power supply

place the motherboard on a piece of card board larger than the motherboard,

this will eliminate a short from the mobo to the case which could be a possibility

Install the cpu with, 1 stick ram in dimm 1, power supply, case switch and case speaker
Connect ps2 mouse and keyboard along with the monitor
Repeat the above and power on

If the computer now boots into bios you most likely had a case short so make sure when installing the motherboard in the case that you use standoffs and they line up with the mounting holes in the motherboard and none of the standoffs touch anything else on the underside of the board.
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#3
tybee

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Thanks for the quick response. First an edit to the original post: the components going into the upgrade are Azus AX78 mobo, AMD 64 x2 6400 cpu, Diamond 3870 video card, and a thermaltake TR2-430 ps. The legacy: WD 1600 hd, (2) dvd RWs and a floppy drive. Case is of ukn mfgr.

I tried the two steps you suggested with lackluster results but a possible lead. For step 2 I first removed the video card and decided to check again minus the card and Whalla the cpu fan stayed on. So plugged the system fan back in tried again... no go. So I went on to cardboard test with no results except that I attempted bending the board and got a repeat of the cpu stays on result. It only happened the one time (so far) and can't remember if quit when I relaxed the board or not so I'm going to examine the mobo with a magnifying glass. If you have some more steps please advise, I'm monitoring for your posts. Thanks again.
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#4
happyrock

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it could be the power supply is not putting out enough juice...
does the video card require a separate power connector to it...
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#5
tybee

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yes but these components are not new. They have operation in my other computer for a little over a year now. Including the power supply.
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#6
tybee

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Another update. I have found a spot in the center of the mobo that with applied pressure (eraser tip) the cpu fan will come on and stay on. Mobo is still on cardboard with all peripheral disconnected. Interestingly it will stay on that point when I release the pressure.
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#7
rshaffer61

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Unless I'm reading something into this it sounds like you may have a problem with MOBO.
Unless the connector for the fan is at the spot or near the spot you are pressing on. In this case it may be a faulty connection.
Happyrock what do you think?
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#8
happyrock

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Unless I'm reading something into this it sounds like you may have a problem with MOBO.
Unless the connector for the fan is at the spot or near the spot you are pressing on. In this case it may be a faulty connection.

I agree...
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#9
tybee

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Yet another update. With the mentioned results I went ahead and reconnected the mobo peripherals and booted up while pressing the "soft spot" just long enough to get it over the hump. The mobo has a POST display and it went to FF which the book says is a boot attempt. However at that point the monitor only displayed a "power save" mode and won't get past it when I hit the keyboard or click the mouse. This reminded me that recently I ran into that same problem while on the computer that these components came out of. I could not get it to move past that "save mode" display then either and solved the problem by rebooting and then adjusting the power save settings to "never". The soft spot is almost dead center... its between the video card and the south bridge(?). Right on the AX78 nomenclature. You think I need to replace the mobo (dread $).
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#10
tybee

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Last post on this issue. I ordered a new mobo. I want thank you again for the assist, it brought rapid (if undesired) closure. Thanks again.
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#11
rshaffer61

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We will continue to monitor this topic until you have installed new MOBO and verified that this indeed has resolved your issue.

Also if you need assistance in installing new MOBO to make sure there is no possibility of shorting it out let us know.
We are here till the end. :) :) :)
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