Real hardware problem this time - computer won't boot

  • Thread starter Thread starter Cyde Weys
  • Start date Start date
C

Cyde Weys

This is not my week when it comes to computers! Argh!

Anyway, my old ECS mobo crapped out for the second time, so I said,
screw this, I'm going with Asus. I bought an Asus A7V8X-X and a stick
of 512MB DDR-RAM, 333Mhz FSB, PC2700. I tried assembling my new
computer, and to put it simply, it doesn't work. As soon as I flip the
power switch (not the circular button on the front of the case, I'm
talking about the 1/0 button on the ATX power supply), the system hums
into action, the fans all turn on, and things start happening. Then, a
few seconds later, the power just abruptly cuts off.

Here are the full hardware specs in case it helps any:
450W ATX PS
2100+ Athlon CPU
512MB PC2700 333Mhz FSB DDR-RAM
Iomega internal 4x/2.4x DVD+RW drive
floppy drive
40GB 5400 HD
56X CD-ROM drive
Radeon 9000 Pro videocard

I tried to keep as many things constant as possible while switching out
the mobo. The only changes I made besides the RAM was plugging in the
speaker/IDE LED/power switch, etc. indicator lights & switches. I
tried, to the best of my ability, to put them in correctly according to
the manual. I don't think that them being in the wrong slots would keep
the whole system from booting - it would just stop those lights from
working, right?

Anyway, I tried taking out all of these little wires except for the
power switch. Still a no-go. Upon flipping the ATX power switch, the
whole system turns ON, which is unusual, because previously this
computer required the switch on the front to be pressed before it
actually turned ON. Could this be the cause of the problem - and anyone
know how to fix it? Thanks in advance for the help.
 
V said:
The power on leads from the MB may be constantly shorted together. This will
cause the "instant on" when you put power to the ATX power supply. The MB
then thinks you're holding the power button on, and shuts down after a few
seconds. Try removing *all* connections from the front panel to the MB.
A momentary short of the "POW-ON" MB connectors should result in a normal
start-up. If this works, replace the leads in pairs, a set at a time.
The MB manual should show the polarity of the front panel lights. If the
LEDs don't lite up when they should, reverse the leads to the MB connector.

It could be a defective power switch on the front panel, but it's more
likely the wrong MB leads were used. Even a LED on the front panel could
look like a *short* to the "POW-ON" connectors at the MB if it were connected
by mistake.

Cross check the MB manual with the actual MB, and look carefully at the
designation on the case front panel leads.
Click to expand...

I tried disconnecting all the leads and I still get the same symptoms.
What could cause this computer to think the power button is continually
being depressed, and thus shut down a few seconds after startup?
 
Me said:
The A7V8X has CPU overheat protection. Chances are, you're heatsink is
backwards or otherwise misinstalled. I had this happen about 3 days ago.
Click to expand...

Thanks for the advice. I'll try re-seating the heatsink and see if that
fixes anything.
 
Cyde said:
I tried disconnecting all the leads and I still get the same symptoms.
What could cause this computer to think the power button is continually
being depressed, and thus shut down a few seconds after startup?
Click to expand...

A short from the MB to the case can sometimes cause this. Make sure any
metal stand-offs are only on the MB printed circuit "pads" that are meant
to be grounded to the case. Check any wires or metal pieces that may be
contacting the MB.

Also you might want to try it with only CPU, memory and video card
installed. That should get you through the POST tests. If that works,
add a floppy with a boot-disk and see if it boots into DOS properly.
Then add the CD-ROM and install the MB drivers that came with the new
mother board.

I've known a few people that went so far as to remove the MB from the
case entirely and try it standing alone on an insulated board with the
motherboard plugged only into the power supply.

Good luck!

Virg Wall
 
Cyde said:
This is not my week when it comes to computers! Argh!

Anyway, my old ECS mobo crapped out for the second time, so I said,
screw this, I'm going with Asus. I bought an Asus A7V8X-X and a stick
of 512MB DDR-RAM, 333Mhz FSB, PC2700. I tried assembling my new
computer, and to put it simply, it doesn't work. As soon as I flip the
power switch (not the circular button on the front of the case, I'm
talking about the 1/0 button on the ATX power supply), the system hums
into action, the fans all turn on, and things start happening. Then, a
few seconds later, the power just abruptly cuts off.

Here are the full hardware specs in case it helps any:
450W ATX PS
2100+ Athlon CPU
512MB PC2700 333Mhz FSB DDR-RAM
Iomega internal 4x/2.4x DVD+RW drive
floppy drive
40GB 5400 HD
56X CD-ROM drive
Radeon 9000 Pro videocard

I tried to keep as many things constant as possible while switching out
the mobo. The only changes I made besides the RAM was plugging in the
speaker/IDE LED/power switch, etc. indicator lights & switches. I
tried, to the best of my ability, to put them in correctly according to
the manual. I don't think that them being in the wrong slots would keep
the whole system from booting - it would just stop those lights from
working, right?

Anyway, I tried taking out all of these little wires except for the
power switch. Still a no-go. Upon flipping the ATX power switch, the
whole system turns ON, which is unusual, because previously this
computer required the switch on the front to be pressed before it
actually turned ON. Could this be the cause of the problem - and anyone
know how to fix it? Thanks in advance for the help.
Click to expand...

By disconnecting all the drives and front-panel LEDs/switches, I can now
get the computer to stay on indefintely, so I suppose whatever was
causing the short is now fixed. However, I'm having a different
problem: it doesn't ever send anything to the monitor. I guess I'll
have to plug the speaker in to see if it POSTs.
 
Cyde said:
Ehh, what are metal stand offs and these circuit pads you speak of?
Click to expand...

Just how did you mount the motherboard into the case?

The metal stand-offs are hexagonal metal pieces about 1/4' long, with a
threaded stud at one end which screws into MB mounting holes on the
case back-plane. The other end is threaded to accept a mounting screw.

On the back of the MB there are metal "pads" (exposed circuit board trace),
designed to be placed on the stand-off with a mounting screw through the
board. This grounds the MB only where it should be grounded to the case.

I've seen systems with only the little plastic stand-offs thru holes in the
MB and into slots in the back plane. This doesn't ground the MB, but
is much better than grounding it where it's not supposed to be grounded!

I've even seen systems with the MB screwed directly to the backplane!
A few even worked!!

The black wires from the power supply are ground wires, but at high frequencies
a better ground is needed, hence the mounting "pads" and the metal stand-offs.

If you had no metal mounting hardware, you'll have to look elsewhere for
a possible short to the case in the wrong place. Are there metal mounting
screws that hold the board in place?

Virg Wall
 
Back
Top