IBM NetVista Power Supply problem

Run that by again...
Two HP-M1854F3P do not work
and
Two known good standard PSU's do..
????

Is either HP-M1854F3P known good?
Have you changed video cards? .. added drives? .. added cards?

What model of NetVista?
There's gott'a be 20+ versions.

HP-M1854F3P is only 185 watts.
Pretty much if you've upgraded anything you may have run out of 'juice'.

maybe a connector problem?  verify the pins

PCBONEZ & nobus: Sorry I wasn't clearer the first time. The NetVista model is a MT-M 8307 22U. It is using the integrated video and has no added-on components. I've tried it with and without drives connected to the PSU.
The system came with the model HP-M1854F3P power supply. I ordered a replacement, which gave me the same result. System powers on, but no picture. I ordered another HP-M1854F3P from a different vendor, same result. Then I tried a stock, non proprietary ATX PSU and it all works with that one hooked up. To be honest, both of the PSUs ordered from the vendors were not new and it could be they are bad. My pocket tester indicates one bad rail on all of the HP-M1854F3P units- the -5V. But one of the vendors said that shouldn't matter. It's not used anymore on modern systems. But I'm wondering if IBM is straying from their own standard. The -5V is good on the PSU that does work in the sytem.
No pins have been altered.  Right now, I suspect the vendors have sent me bad power supplies, but I can't believe they would do that, especially since they said they tested before they shipped.
Any other ideas would be appreciated. Thanks.

HP-M1854F3P are manufactured by Hipro who generally makes very good PSUs [they build almost entirely for major OEM's and not for retail] but now and then they resort to unreliable capacitors.
-
With it unplugged, I would open one up and inspect [with a flashlight] for bad capacitors and anything the looks like it's overheating.

PSUs with blown caps can generally be rebuilt for under $15 in parts by someone with basic soldering skills. Biggest thing is making sure you get the right grade of capacitor. I can help with that or the folks over in www.badcaps.net forums can too.

There is also a fuse inside the PSU somewhere but it may be soldered on and/or covered in shrink-wrap so it doesn't always look like a fuse at first. [A designation beginning with an 'F' on the PCB is a giveaway.]

Also check the actual connectors for power-to-mobo connections.
If they used ill fitting connectors they may have burnt or oxidized inside in the contact area.

.

HP-M1854F3P are manufactured by Hipro who generally makes very good PSUs [they build almost entirely for major OEM's and not for retail] but now and then they resort to unreliable capacitors.
-
With it unplugged, I would open one up and inspect [with a flashlight] for bad capacitors and anything the looks like it's overheating.

I checked for blown caps on the mobo. They all look like new. In fact the whole system looks pristine.
As I mentioned before, the system runs fine with known-good, stock PSU.

PSUs with blown caps can generally be rebuilt for under $15 in parts by someone with basic soldering skills. Biggest thing is making sure you get the right grade of capacitor. I can help with that or the folks over in www.badcaps.net forums can too.

There is also a fuse inside the PSU somewhere but it may be soldered on and/or covered in shrink-wrap so it doesn't always look like a fuse at first. [A designation beginning with an 'F' on the PCB is a giveaway.]
Thanks for this tip. I've thrown away a lot of PSU's thinking they're not salvageable.

Also check the actual connectors for power-to-mobo connections.
If they used ill fitting connectors they may have burnt or oxidized inside in the contact area.
Yes, I inspected around the conectors and looked for corrosion or signs of overheating, but it's all very clean. Besides, it works o.k. with a stock ATX power supply.
 I'm thinking at this point, I'm just going to transfer everything to another case that can accommodate the standard PSU. I hate to waste a case, but unless there are any other ideas, that looks like my only option right now. Thanks again.

Mahalo for your advice. i did end up putting the system into an old extra case I had laying around. I had to get this done for the customer. He was waiting two weeks for these power supplies to come in. It takes a long time to ship to Hawaii and it's expensive. I wound up eating it on this one. Thanks again!

I ended up putting the system in another case that accommodates regular size power supplies. IBM's approach, as we know, has been a little different from the standard sometimes. Personally, I'm glad they're out of the personal computer market now. It's kind of rare to run into this problem on regular worksations now.