Replacing PSU on an old Dell

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Replacing PSU on an old Dell

Postposted on Thu Dec 20, 2012 12:58 am

I have a Dell Dimension 8400 in the closet as my current file server. It's a Pentium 4 at 3.0ghz. I want to add a couple harddrives to it, but the current PSU lacks enough connectors, and likely enough juice to handle all the drives. I have a space PSU sitting right next to me, but I know that old Dells have proprietary PSU connections. So I'm hoping this isn't that old and it will work fine, but I thought I'd ask the knowledgeable commentariat at TR before doing anything.
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Re: Replacing PSU on an old Dell

Postposted on Thu Dec 20, 2012 10:57 pm

C'mon, know one knows? Or even just knows how to find out?
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Re: Replacing PSU on an old Dell

Postposted on Thu Dec 20, 2012 11:22 pm

If my Google-fu works, your Dell's got a 24-pin main connector, yes? If so, it's got a standard connector and you can use any 24-pin compatible ATX p/s.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 1:23 am

Anything from dell from the p4 era should work just fine with a regular atx psu as long as it isn't a special form factor like sff or blade type server psu. I haven't seen proprietary atx shaped stuff from them since the pIII days in their regular consumer/business desktop lines. Back then it was a huge pain bc they had a normal looking 20pin connector but with a few wires in different places. So if you hooked up a regular psu and turned it on you would fry the board and the psu. :o
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 5:07 am

I'd be tempted to use SATA power splitters.

Hard drives are only a few watts each, even under load. If you want to add only two more, you'll be increasing your load on the PSU by a whopping 12W or so, and Dell would never leave that little headroom in their PSU. If your PSU assplodes because of an extra 12W, then it was way past due for replacement anyway!
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 12:08 pm

Thanks all.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 12:23 pm

Chrispy_ wrote:I'd be tempted to use SATA power splitters.

Hard drives are only a few watts each, even under load. If you want to add only two more, you'll be increasing your load on the PSU by a whopping 12W or so, and Dell would never leave that little headroom in their PSU. If your PSU assplodes because of an extra 12W, then it was way past due for replacement anyway!

The steady-state draw isn't the concern. The most likely time for problems to occur is when the system is initially powered up and all of the drive spindles try to start at once. Spin-up power draw of a hard drive can easily be several times what the drive uses in normal operation.

Given that it is a file server, power-cycling the system should be a relatively rare event though.

If the power turns out to be a problem, another potentnal option would be an eSATA card and a couple of external eSATA drives...
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 12:37 pm

Chrispy_ wrote:Hard drives are only a few watts each, even under load. If you want to add only two more, you'll be increasing your load on the PSU by a whopping 12W or so, and Dell would never leave that little headroom in their PSU. If your PSU assplodes because of an extra 12W, then it was way past due for replacement anyway!

Well, yeah, but in scenarios like this the problem isn't necessarily that it goes a-splod-y, but that it goes slightly unstable under peak demand loads and there's no obvious sign as to why.

OTOH if this is running as a file server then the graphics load probably never peaks anyway, so there's probably some headroom on that side of things.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 2:04 pm

I do remember that there was once an issue where Dell used the standard connector but reversed some wires, making the motherboards incompatible with ATX spec power supplies and risking damage if used. I just don't remember how long ago that was, or what systems were affected.

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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 5:47 pm

I replaced the PSU on a PC just like that a few months ago, I used a Corsair CX-430 because it was the cheapest I could find. The only problem I had, and this may just be this particular PC, was that it wouldn't power up until I installed a PCI card, anything, as if there wasn't enough draw or something to send a signal to the PSU. I plugged in a very old PCI video card, or a Soundblaster, I can't remember, and that did the trick. It's been working like a champ ever since.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 6:21 pm

hp9000 wrote:I replaced the PSU on a PC just like that a few months ago, I used a Corsair CX-430 because it was the cheapest I could find. The only problem I had, and this may just be this particular PC, was that it wouldn't power up until I installed a PCI card, anything, as if there wasn't enough draw or something to send a signal to the PSU. I plugged in a very old PCI video card, or a Soundblaster, I can't remember, and that did the trick. It's been working like a champ ever since.

Well that's strange. But not entirely crazy. Over the years, the percentage of power drawn from each rail has shifted, from the 3.3V and 5V rails to the 12V rail. Depending on the design of the regulators in the PSU, things may not work right if certain rails are unloaded. So matching an old system with a new PSU sometimes does not work.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 6:25 pm

the percentage of power drawn from each rail has shifted, from the 3.3V and 5V rails to the 12V rail. Depending on the design of the regulators in the PSU, things may not work right if certain rails are unloaded. So matching an old system with a new PSU sometimes does not work.


Yes, the new have 100% of the rated available on the 12v rails.
Going back this far the distribution would be much different.
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Re: Replacing PSU on an old Dell

Postposted on Fri Dec 21, 2012 6:43 pm

IIRC a couple of years ago I solved this issue by sticking a floppy drive into a system with an older motherboard that wasn't making its (newer) PSU happy. Using old tech as a dummy load... :lol:
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