20 pin power plug in a 24 pin M.B. plug

Hi all, My friend has a MS-7613 M.B. and the computer stopped working. (Won't turn on) So I said lets put a new power supply in. I looked up the board on the internet and it said 24 pin connector. I bought a power supply and took it over and when I opened up the case it did have a 24 pin connector but the power supply plug was only 20 pin. Is this right or did HP screw up building this. Could it have caused the MB to baff out?
I changed the power supply and it still won't turn on. If you hit the power button the fans twitch maybe 1/4 turn and nothing else happens. I checked the old power supply to see if it had the 4 pin plug that goes with the 20 pin and it didn't.
Thanks In Advance
Dave

It is possible to run a 24-pin motherboard with a 20-pin PSU.

http://www.smps.us/20-to-24pin-atx.html

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The four pins that you are leaving open are just redundant pins for higher current capability

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I'm assuming you remembered to plug in the 4-pin ATX12V in the socket by the CPU.

Yeah got the ATX12V.
Do you think the board is toast?

It's possible. Did you try reseating the ram as well?

I doubt a MB that new has bad caps, but it's something to check.
http://www.badcaps.net/

Post the make and model of the old power supply. Sometimes, when an el cheapo power supply fails, it can take out the motherboard as well.

Yeah reseated the RAM and unplugged all peripherals just in case. I have seen a bad CD-ROM stop a computer from booting up.
I didn't see any bad caps but sometimes they don't show.
Thanks
Dave

Bestec ATX-250-12Z Rev. D7R
Dave

I really think 250W is way to low for newer boards?

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Bestec

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Yikes. Those are some of the worst. 250W is pretty low nowadays.

Bestec - there is your answer. The motherboard is almost certainly fried. When Bestec power supplies fail, 99.9% of the time they take out the motherboard.

Bestec is OEM power for a lot of PC manufacturers, or used to be. Lord knows why unless it's the price. At any rate, before tossing the mobo try buying a real PSU with a 24- or 20+4 pin connector. While some 24-pin boards will run with only 20 pins connected I have seen plenty that will not do so.

P.S. I had to look at the date of this thread to make sure I wasn't necromancing. 20-pin PSUs are pretty old-school stuff now.

Thanks lgbpop, But as I stated at the beginning of the thread we tried a new PSU and it still didn't turn on.
Thanks
Dave

Fried mobo :(

This is a good illustration of why I always urge people to pay the extra for a decent PSU when building a PC or replacing a power supply. Good quality ones still fail sometimes, but they do so gracefully. I've had 4 PSU failures over the last 11 years, but they were all good brands, and not one of those failures affected any other component.

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Originally Posted by lonewolf

Thanks lgbpop, But as I stated at the beginning of the thread we tried a new PSU and it still didn't turn on.
Thanks
Dave

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Sorry, guess I misunderstood. I understood the post to say the new PSU you tried was a 20-pin connector plugged into a 24-pin header.