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Replacement PS does not work with MB OR Case?

By IT cowgirl ·
My power supply finally died. It was a 200w or 250w. I could not find another (of course) and purchased a 300W ATX power switching PS which has both 20/24 pin compatibility.

When I plug in the new PS the machine never boots, however the PS powers up and then begins "switching" immediately (running fast, then slow, then fast...). Simultaneously, the lights on the case and keyboard flash on/off in unison with the PS.

I have an older ATX micro generic MB with an AMD Athlon chip. I have scoured the internet for documentation and was only able to find basic specs. This is a 20 pin power receptacle on the MB.

I am thinking the case is the problem and not the MB. This case was setup to handle both AT and ATX MBs. When I upgraded to the current MB (way back when) and went to W2K and then WXP, the OS shuts down normally, but then the old "it is OK to now shut off your computer"
splash screen comes up afterwards and I must hold the power button until it powers off.

Any ideas or thoughts as to whether this is resolved by a new case or is it time for a new MB?

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All Answers

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Inspect the motherboard

by TheChas In reply to Replacement PS does not w ...

Your computer and OS do not know what type of case you have.

The "it is now safe to turn off your computer" message is common with Windows XP and 2000. The usual cause is that ACPI mode is not enabled in BIOS setup. Sometimes, Windows fails to enable ACPI mode when it sets up the system drivers.

But, back to your main problem, carefully inspect your motherboard. Look at the capacitors near the CPU and power connector. If any of these are bulging out or leaking fluid, that is the cause of your problem.

A slow spinning fan could also be at fault too.


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MB is OK

by IT cowgirl In reply to Inspect the motherboard

Yes I checked the MB and it is OK, in fact it was running fine when I discovered the fan in the PS was not working. That is what prompted me to purchase a new PS.

Trying to determine if it is the case or MB which does not work with the PS. Hopefuly not both!

And thanks for the ACPI Bios tip, it had not accorded to me! I always check it on laptops but do not think about it on desktops. Duh!

Great tips, just not the right answer yet.

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by TheChas In reply to MB is OK

That is puzzling.

Did you check the AC input voltage switch?

You might also check the motherboard and drive connectors to make sure that a line is not swapped somewhere. The wire colors should match those on your old power supply.

Finally, it is possible that you got a bad power supply. It does happen.


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I will check it!

by IT cowgirl In reply to Puzzling

I also have another new PS I can try.

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PS Dead MB ?

by newdays007 In reply to I will check it!

A friend had an E machine - stopped booting up. I looked at it - Noticed the same as you!
250W PS fan stopped working - Bought a replacement 300w ATX PS from Comp USA.
PS Fan working - CPU fan not working - PC won't boot. Pulled the 4 wire Power connector from the mother BD and CPU fan started up. PC had flashing light on front panel and I believe steady beeps. (I didn't check the old PS wiring against the new PS but I will and report back. I figured it was the PS took out the Mother Bd -- Before I replace the MB I will remove different components CD - DVD and so on.

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was still booting

by IT cowgirl In reply to PS Dead MB ?

I was having HDD slowness issues and ran a program which determined there was too much heat. Checked the PS and discovered the PS fan did not work. Replaced the PS fan but PS fan did not work, although PS did allow the computer to boot OK. Which is why I purchased a new PS.
I am now trying the other PS I have.

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Bad PS!

by IT cowgirl In reply to Puzzling

You were correct, the new PS was bad.

Luckily the other PS I bought worked fine and it is a 500W! Coolness!

Thanks for the idea, great work!

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by TheChas In reply to Bad PS!

It is great to have the feedback and know that we helped you fix your problem.

I went through a run of bad power supplies a few months ago. It is very frustrating when you can't trust that a new part is good.

Happy computing,

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