For a change it isn't OldFatGuy posting here with hardware related woes, but now a problem beyond my grasp of understanding computer hardware has occured.

Some background information follows, for links see below:
The thing is that I have an old PC lying around I'm currently not using that I want to repurpose as a Windows XP and 7 machine, while my newer system will migrate to Windows 10.
For this I did some research on my old PC's motherboard(1) and ordered this CPU(2), which is almost the fastest it can handle. Also I bought some extra RAM modules so I now have 4x 2GB for a total of 8GB, complete overkill for 32bit Windows XP I know, but should come in handy for Windows 7 x64.
I already had a graphicscard(3), which incidently is the newest GPU series still supporting Windows XP and found an identical one on a dutch hardwarewebsite so I can put them in crossfire.
To install Windows XP and Windows 7 on I bought these two SSD's(4) backed up by a pair of HD's(5) I already have.
To power it all I thought it would be prudent to retire my trusty old 300W PSU and replace it with this 550W(6) unit.
Background information ended.

And here the mystery begins to unfold.
As I was still waiting for the CPU, RAM and graphicscard to arive I already got the SSD's and PSU which are new.
Enthausiastically I installed the new equipement, carefully connecting it all to the new PSU.
And then when I pressed the powerswitch in high anticipation, but with a casual cool as I have operated the guts on this machine more than I can count..... to my astonishment nothing happened!
Pressing the powerbutton once more I noticed the CPU fan turned once and the powerled lit up briefly only to die immediately afterward.
As I was still recovering from this unexpected result I was going through my options, which were unplugging everything except the mobo+cpu connectors, but still my PC remained dead with only a motherboard with 2 RAM modules.
Then I pulled out my old PSU on the same system and low and behold it all worked!
So my suspisions were correct and it was that damn new PSU so I immediately called the online store I got it from and they agreed that I send it back for them to check if the unit was faulty.
Which I did but then yesterday I got a call from them telling me they tested it and nothing was wrong with it and now they've returned it and now here I am with a suposedly working PSU but still my system remains dead when I connect it.

What I still need to do is connect the new PSU to my other PC to see the result, but even if it works on that PC it still mystifies me why it doesn't on the PC in question.

Already I did some fruitless searching on the web but I thought maybe you people might have the answer since you are a bright bunch of boys and girls.
By the way, helpful answers will be rewarded with a game from my tradelist.

Also I will be away for a few days fixing my brothers roof so I probably won't answer before two days from now (yes I have a smartphone but I hate typing on the damn thing).

edit:
Since the links are all screwed up I put them here.

(1) https://www.msi.com/Motherboard/K9A2_CF

(2) [url=https://www.ebay.com/itm/AMD-CPU-Phenom-II-X2-550-Black-Edition-3-1GHZ-Socket-AM3-HDZ550WFK2DGI/183037036843?epid=74102078&hash=item2a9ddb892b:g:EngAAOSw-K9ZJ08L]https://www.ebay.com/itm/AMD-CPU-Phenom-II-X2-550-Black-Edition-3-1GHZ-Socket-AM3-HDZ550WFK2DGI/183037036843?epid=74102078&hash=item2a9ddb892b:g:EngAAOSw-K9ZJ08L[/url]

(3) http://www.sapphiretech.com/productdetial.asp?Pid=7B0415DF-2F7F-41C8-B923-016078FD642E&tag=download&lang=eng

(4) https://www.kingston.com/en/ssd/consumer/sa400s37

(5) https://www.amazon.de/Seagate-Desktop-interne-Festplatte-SATA/dp/B005T3GRNW

(6) http://www.coolermaster.com/powersupply/80-plus/mwe-bronze-550/

Had a similar issue earlier in the year, only to come to the conclusion that the motherboard was dead. You will have to eliminate other components as being the issue, but to me it doesn't sound any different than what happened to me. I will say that indeed the motherboard was dead for the rig I was building.

The thing is I can still run the old config, mobo, cpu, gpu and the and it all works with the old powersupply, I can boot BIOS and install an OS no problem but with the new PSU....nothing.

When I have time I will test it on my other PC but I have to go to bed now.

maybe RAM compatibility?

Yeah, I missed that part. The new PSU indeed sounds faulty if you can attach an older PSU and have everything working properly.

Does the new PSU use the same connectors as the old one?

Compare stats/features of old and new PSU. Maybe there is a signal check on the new PSU that fails on the old mobo, and the old PSU does not have.

Another thought is that older PSU's were designed to carry a higher load on the 5v rail, and newer PSU's carry a higher load on the 12v rail. Could your old mobo be drawing too much 5v from the new PSU?

I notice that your mobo site has a Compatibility page. https://www.msi.com/Motherboard/support/K9A2_CF#support-test

Id guess on something related to the startup signal (for the PSU) as well, maybe the old one is a bit more sensitive.

Does the board have a buffer battery for the CMOS chipset somewhere? Could be broken if it hasn't been used in several years, might be worth to exchange it. I unpacked an old computer (Powermac, but shouldn't really matter) a while ago and it wouldn't startup either before I replaced it.

According to the msi website, your motherboard requires one of the latest bios available for it, but it shouldn't be a problem since you said that with your other PSU, it worked. So one of the latest bios must already be installed.
You didn't write your RAM specs. Once again, it shouldn't be the cause of the problem, but it never hurts to know its speed. Check that the stick are all the same.

I would blame the PSU.


This may sound very very stupid but... did you plug the new PSU correctly ? Could one of the cables have been misplugged / not fully plugged ?

Strange,

I hooked up the Coolermaster MWE500 to my new computer and it does work.

Then I connencted the PSU that was in my new PC (Corsair CX600) to my old one and it also works, so I swapped them for the time being which is a bit of annoying as the Coolermaster doesn't have enough connectors to hook up all the drives.

I'm going to try to sell the Coolermaster and try to get a 2nd hand Corsair then at least I know it will be working.

Though I still don't understand why the Coolermaster isn't liking my old PC. :/

My guess it that some part of your old mobo is not compatible with the Coolermaster's protection circuitry.

That's probably it, thing is I already run the latest BIOS.

I'll mark you as solution as you can use a rep boost but you have to share it with Tcharr. :)