New Motherboard/CPU--System Will Not Power Up?

[Com Crumb]

I had need to upgrade my old motherboard/cpu for a processor with the
SSE2 instruction set and I didn't want to upgrade my AGP card for a
PCIe card (which greatly limited my mobo choices).

Old CPU: Athlon XP 2800+
Old Mobo: MSI KT6 Delta

New CPU: Pentium D 915 (2.8 GHz)
New Mobo: ECS P4M800PRO-M

Every other component remained the same:

Case & PS: Antec/Antec 430W
Video: Matrox Millenium P750
RAM: 1.5GB PC2700 DDR333

The problem: Will not power up. Occassionally (very randomly--something
on the order of one out of 20 tries), when hitting the front power
switch, the fans will spin for a flash. When I say fans, I mean all the
fans--the video card, the cpu, the power supply, the case fans. And
when I say for a flash, I mean that they don't even get a chance to
emit any noise whatsover--it's like they just get a kick of juice and
then nothing. The inertia from the kickstart will of course allow the
fans to spin for a couple of seconds although they are obviously not
getting power.

One possible issue: My power supply has the older 20-pin connector and
the motherboard has a 24-pin connector. The mobo came with four of the
pins taped over, as if to accomodate my own connector. I left the
"extra" four pins taped over, and my old connector seems to fit in the
other 20 pins just fine.

Another thing: My case is a full ATX tower. The board is designed for a
Micro ATX case.

Anything I should do to troubleshoot? I've homebuilt several systems,
but I've never had the won't-power-up problem. It's been awhile since
I've done this, so I suppose it is possible that I'm missing something
totally obvious, but I've spent hours staring at this thing.

Thanks for any and all help.

 

[Rod Speed]

I had need to upgrade my old motherboard/cpu for a processor
with the SSE2 instruction set and I didn't want to upgrade my AGP
card for a PCIe card (which greatly limited my mobo choices).

Old CPU: Athlon XP 2800+
Old Mobo: MSI KT6 Delta

New CPU: Pentium D 915 (2.8 GHz)
New Mobo: ECS P4M800PRO-M

Every other component remained the same:

Case & PS: Antec/Antec 430W
Video: Matrox Millenium P750
RAM: 1.5GB PC2700 DDR333

The problem: Will not power up. Occassionally (very
randomly--something on the order of one out of 20 tries), when
hitting the front power switch, the fans will spin for a flash. When
I say fans, I mean all the fans--the video card, the cpu, the power
supply, the case fans. And when I say for a flash, I mean that they
don't even get a chance to emit any noise whatsover--it's like they
just get a kick of juice and then nothing. The inertia from the
kickstart will of course allow the fans to spin for a couple of
seconds although they are obviously not getting power.

One possible issue: My power supply has the older 20-pin connector and
the motherboard has a 24-pin connector. The mobo came with four of the
pins taped over, as if to accomodate my own connector. I left the "extra" four
pins taped over, and my old connector seems to fit in the other 20 pins just fine.

What did you do about the separate 4 pin square power connector ?
Thats essential, it wont start without that.

Another thing: My case is a full ATX tower.
The board is designed for a Micro ATX case.

Doesnt matter as long as it fits fine.

Anything I should do to troubleshoot? I've homebuilt several systems,
but I've never had the won't-power-up problem. It's been awhile since
I've done this, so I suppose it is possible that I'm missing something
totally obvious,

Yeah, most likely that 4 pin square power connector.

 

[Com Crumb]

What did you do about the separate 4 pin square power connector ?
Thats essential, it wont start without that.

Thanks for the reply, but the 4-pin power connector is definitely
plugged in.

 

[Paul]

Thanks for the reply, but the 4-pin power connector is definitely
plugged in.

That could be overcurrent on the power supply. The new motherboard
may have a short, or you have a standoff touching a metal conductor
on the bottom of the motherboard. Each brass standoff should line
up with a tin-plated hole on the motherboard. If a standoff is
installed, where there is no hole in the motherboard, that
standoff should be removed (and pray there is no permanent
damage).

Try the following.

1) Install CPU, heatsink, fan on the motherboard. Connect the fan
cable to the motherboard CPU fan header.
2) Connect motherboard to power supply. Connect the 20 pin connector
to the 20 pins exposed on the main connector. Plug in the 2x2
square connector.
3) Connect the case power connector to the PANEL header. Connect
the computer case speaker to the PANEL header.
4) Plug power supply to the wall. Switch on at the back.
Push the power button on the front of the case.

The result should be:

1) Fans spinning and continue to spin.
2) Computer beeps the speaker and the beep code reports that
the RAM and/or video card are missing.

If you don't get that far, the next most likely culprit is
bad motherboard. The processor is least likely to be bad.
Motherboards don't get nearly enough testing at the factory.

You can verify the power supply by connecting it to the
old system.

Paul

 

[Com Crumb]

That could be overcurrent on the power supply. The new motherboard
may have a short, or you have a standoff touching a metal conductor
on the bottom of the motherboard. Each brass standoff should line
up with a tin-plated hole on the motherboard. If a standoff is
installed, where there is no hole in the motherboard, that
standoff should be removed (and pray there is no permanent
damage).

I've been coming to this newsgroup off and on since 1998 when I built
my first system, and pretty much I've come away each and every time
amazed that this resource exists.

Your hunch about the standoffs was exactly right. I don't know yet if
there is any damage, but at least everything spins up now.

So thank you for your help--and for anybody reading.