Nah, forget the pins thing, I didn't spot that you left the paper clip in. Although shorting the pins will work.

So all the power stuff worked, fans on etc. until you plugged a hard drive in?

Yes... But once I unplugged it again (and I'd had the same HDD on moments earlier no problem) it still wouldn't work. So unless it outright killed the PSU, I dunno.

My mobo has a power button on the board itself so I'm reasonably satisfied the case isn't a problem.

This morning, I tried PSU with paperclip plugged into nothing and it switched on at correct voltages again. Then I went to work. 

When I found myself with a similar dilemma a few weeks ago, I was happy that the motherboard was faulty as the multimeter readings for the PSU were fine and it powered a hard drive, fans etc perfectly well when not connected to the board. It was also a reasonably expensive item even if not quite up there with yours.

However, I decided that I couldn't be sure, and as I hadn't done any PC building for ages I bought a new motherboard/CPU/memory and a new PSU. The old CPU was an early i5 and as compatible second hand motherboards are stupidly expensive, I couldn't reuse it.

I was then left with the old PSU which I used to build a second PC/Server using an old Athlon 64 and motherboard from the I-can't-throw-that-away pile. I learned a lot about the fibs told by Nvidia and several mobo manufacturers about how much memory the early Nforce chipset/bios combo could support (up to 4GB but only if you could find memory modules that nobody actually made) and had fun playing with it until it started making crackly noises and finally the PSU burst into flame with a loud bang.

So my present theory is that the PSU may well have killed the original motherboard by serving up generous portions of voltage at inappropriate moments.

Of course, I then decided to buy an ultra cheap PSU and discovered that I could make use of my old i5 and memory with a new motherboard from Gearbest who manufacture a whole range of boards based on old chipsets for a far more reasonable price than second hand ones fetch on ebay. Expensive things computers.

My motherboard, CPU, RAM and PSU are all second hand from the same bloke, who has the most ridiculous leading-edge kit all the time and sells it on as soon as the bleeding edge moves on. While this means I got good stuff cheap it does leave me with a bit of a replacement dilemma, should I ever get to the bottom of this mystery. I doubt I'll go like-for-like in quality on any of it.

But yeah, first I have to figure out this nonsense. I suppose tonight I'll go through the whole chain again but maybe only plug in the SSD drive and not the mechanical one at first. Or something.

Ok. Set the whole power chain up again. If I plug in everything but the motherboard, and short the ATX pins with a paperclip, it powers on. So, motherboard failing, right? Switched it off again to think about the next thing I can do. Except I just thought "oh yeah, recheck voltage" and went back to it and now it will NOT power on. Wtf? Argh!

Did you try another psu already? Starting to sound like it's your problem.

Would have to buy one to do that I think (though I'll raid the server room at work tomorrow just to check) so I'm trying to avoid it until I'm sure. It is increasingly more likely... But I kinda feel like the motherboard or something on it could yet be the culprit somehow.

After leaving it a while then trying again it switches on and let's me read a good voltage. It really seems that connecting the motherboard is the step that jiggers it and puts the PSU into some kind of safety mode that shuts off the power for a bit.

Maybe it has overheating protection. Does it get noticeably warm?

Nope. Also a cold start plugged in is a fail, but while I've got it running in whatever form I can leave it for plenty of time no trouble.

Your theory looks pretty good. I see that the BeQuiet P8 1200W has several clever protective measures which a broken motherboard would probably trigger - like short circuit/under voltage/over voltage etc. etc. all of which turn the PSU off (and probably keep it off for a while).

http://www.bequiet.com/en/powersupply/10


Edit: not sure that link's right, but I think the tech details are the same.

Edit Edit: the link's OK

Yeah. Looks like. Hm. Nevertheless, I've ordered a PSU, my thinking being that I can potentially be careful about unpacking and connecting it to the minimal setup (including motherboard) and if it still fails, return it. Whereas if I get a new motherboard and that still fails I'm stuck with it.

No luck on a PSU scrounge in the office so it's done. I really hope it is the PSU because the motherboard's current version costs £275 fucking pounds, there is no way that's getting matched. I wonder what level of downgrade I can get without missing something noticeable.

I can't believe you BYO and don't have an old, undead PSU squirreled away.

 :-S

Like I say, small flat, big clear out when the baby arrived. I gave the near-complete remains of my PCs previous incarnation to my brother in law.

Plenty of room for bikes, though.

I have a small shed exclusively reserved for my two plus all their kit, yup. There is actually still a box of PC gubbins around somewhere, but no PSU in there, it's more obscure bits of cabling and whatnot.

Fess up. The super-annuated PSU is buried in a nearby vacant lot with all kinds of valuable shit your wife can't know about/in your bff's broom closet /with the spare tire in your car. STOP FUCKING LYING.

Wow, you keep your bikes in a shed in London and they stay there?

Well, I don't want to jinx it. But yeah, sure. I sank a u-lock into a bucket of cement underneath it and cut a hole in the floor when I built the shed, so they lock to that. But so far as I know, nobody's so much as tried yet.

Many of the bad things people say about London ain't really so!

>>Many of the bad things people say about London ain't really so!

But then again, much of it is! I'll never forget walking to the bus stop and wondering what all the flowers piled up outside a pub was all about. Turns out a 14 year old kid was stabbed to death when he refused to hand over his mobile :|

As for bikes, I've given up trying to own one in Edinburgh until I have somewhere properly secure to keep it. The best one was when I got home one day to notice my bike had been nicked from the stairwell (D-locked to a sturdy railing, they'd chipped the concrete step away to get the railing out. D'oh). The next morning, after the thieves realised how shit the bike was, it was returned to the stair. Managed to keep hold of it another 3 weeks before it was nicked again, this time for good :(