Anyone familiar with the Delta DPS-250AB 18A PSU?

[Adrian_]

Found this in a 2008-2009 mini Atx HP computer and it appears to have a curious two rails design.

On it's label it says "+12V1 = 8A, +12V2 = 14A" The problem here is whether the first +12v rail is only for the main MB connector, while the second one includes the CPU 4pin connector and the MOLEX/SATA connectors

OR

the first rail includes the main MB connector plus the CPU connector while the second rail includes only the MOLEX/SATA connectors?

Second one wouldn't make much sense (the PSU doesn't have a PCI-E power connector) but with this type of small factor PSU's you never know.

As far as I know the first rail always includes the main MB connector.

Is anyone familiar with this type of PSU's? It would be a PITA to open it up and check the board layout, the computer case is real cramped, cables are routed well and the PSU appears to have many screws on all sides

Thanks a lot for any help.

[redwire]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Could you use an ohmmeter at the cable ends (Molex, CPU, MB, Sata) to see which rail is tied together? The two +12V rails are probably separate (rectifier)

[Adrian_]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Hi and thanks for the suggestion.

I already tried to measure the resistance between all yellow lines (and black lines as well). They all read 0.6-0.7 ohm. (Yelow to yellow and black to black, of couse)

I will try to measure voltages under load as well. Of course, it's possible that the PSU has two rails but the weaker one is not connected at all, but to figure that out I'd have to remove it and open it up.

[Quaddro]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

for mostly psu, 12v2 is for mainboard connector 24 pin, and 12v1 is for peripheral through sata or molex connector.

so you can safely assume this one is follow that rule too.

[Adrian_]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

I was going to do just that, but the resistance between the yellow lines on the MB connector and any other yellow line in the system (CPU, SATA, Molex) is under 1 ohm.
Is there any other method to check, except for opening up the PSU?

[momaka]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

I was going to do just that, but the resistance between the yellow lines on the MB connector and any other yellow line in the system (CPU, SATA, Molex) is under 1 ohm.
Is there any other method to check, except for opening up the PSU?

If all 12V wires show less than 1 Ohm resistance to each other, then the PSU likely has one single 12V rail which then may or may not be "divided" into "separate" rails with current shunts. If that's the case (very likely), then the current limit on each 12V rail is only a "logical" one... meaning, if you pull more than 8 Amps on the rail that is labeled for 8 Amps max, then the PSU may shut down at the very worst.

All in all, though, I wouldn't be too worried about the individual 12V ratings, as the PSU will often allow an amp or two extra through each current shunt (if there are any at all - some PSU's say dual 12V rails but only have one). Just look at the total power/current rating of the 12V rail, and try not to exceed that.

As for testing this without opening the PSU - you will need a load tester that can load each "separate" 12V rail with more than 10 Amps. Once you load the 12V rail that is rated for 8 Amps, the PSU should shut down. If it doesn't, then the PSU doesn't have separate 12V rails.

[Adrian_]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Sadly I don't have a load tester. Probably I should get some beefy resistors and try loading the rails, are there any caveats to this approach?

[momaka]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Nah, don't bother doing that. You will really needs lots of resistors and they would have to be high-power ones too (10+ Watts each at 1-15 Ohms). So the cost for those alone would be more than getting a new PSU.

The easiest alternate ways to load down a PSU is to use NiChrome wire (heating element wire). But again, that would be a whole project in itself. Just use the PSU as is, it would be fine. Only don't go over the total power limit of the 12V rail, that's all.

[Adrian_]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Thanks for the advice. The reason why I wanted to somehow identify the rails is that I'm helping a charity fix some old components and put together usable systems (to be subsequently donated and so on). As you can imagine, there's little time for testing and I wanted to make sure the psu isn't going to die soon due to overload if a video card of about 50w is used.

[momaka]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

It all depends on what CPU you are using and the number of HDDs. If the CPU is just the usual stuff, like Pentium 4, Core 2 Duo, Pentium Dual Core (but not Pentium D), or AMD Athlon 64 or 64 X2.... i.e. around 70-100 Watts power draw max, and you only have 1 or 2 HDDs, then that Delta PSU should be more that fine, even with the 50W video card.

I looked at some pictures of the Delta DPS-250AB-18A PSU online, and it doesn't mention the combined power for the 12V rail. However, the PSU has SATA connectors and specifies two 12V rails, so it's probably a newer design that can handle more current on the 12V rails than on the 3.3V and 5V rails.

Just as a comparison, I've used a 250 Watt HiPro P2507FWP to power an Athlon 64 3500+ (67 Watts TDP) with a fairly high-power GPU (Radeon HD3870, which is rated for about 85 Watts) and two HDDs - all of that for over a year. The total power draw for that PC was about 180 Watts from the 12V rail, which came pretty close to the PSU's 192 Watts rating for the 12V rail (16 Amps). I'm still using that PSU in that PC, but I switched to a low-power GPU just for the summer.

That said, given the vintage of your Delta PSU... if it has any Ltec LZG or LTG capacitors in it, those would be the most likely to fail. And this could happen regardless if you have the 50W video card in there or not. So I would say you can use the video card.

[Behemot]

Re: Anyone familiar with the Delta DPS-250AB 18A PSU?

Usually the first rail is ATX 12 V while the other one is for everything else. There is also some tollerance so it most likely won't trigger till 10 A or so. That gives you plenty room to run 95W (TDP) CPUs. Would not push it to 125W ones.

Also these ancient Delta's usually had only single big +12V cap and not a whole Pi filter. The later ones had two caps and yet later they finally got full filter.