((((WmA)))) An intermittent fault is the worst. It could still be an inadequate or dying PSU, managing to boot a less power-hungry system, but falling over as the more demanding one boots, and the failure expressing as a failure to adequately power various components more or less at random. A new PSU isn't the most expensive item and it sounds as if it could do with replacement soon even if it's not, ultimately, the guilty party.

Although your symptoms aren't anything like they ought to be, it might also be worth swapping out the BIOS battery, if only because it's cost-free.

Have you tried to see if it will post without a drive in? Sometimes the SATA addressing can get messed up (my fanciful attempt at an explanation), and if you move the drive to another plug on the MB AFTER posting with no drive connected. Anyway it worked for me once or twice for hdds on two different-gen mobos. Maybe it makes the bios reset, I dunno, I'm more of a trial-and-error type of fixer.

I put a new battery in when I changed the case. And, yes, I know it could still be the PSU :(

It successfully powered my other PC though, which is fairly well loaded with components - i7 with loads of drives. 

Yep, tried it with no drives. Booted to the BIOS once then failed to boot when I turned it off and on.

OK - had another go with a totally rebuilt, minimal, PC. Still no POST. Swapped the PSU into the Plex server again and it works perfectly.

Off to PCpartpicker!

Just to complete the story, I am now chugging along with a Ryzen 5 3600, MSI B550 Mortar, EVGA 1660 Super, and 16GB of Corsair Vengeance 3600 memory. PSU still holding out.

Very nice!

I haven't dared to look at my bank account recently.

I got a discount on the mobo by buying from Amazon "used but as new". Well, it wasn't exactly that, because some dickhead had rammed a front USB plug in, probably backwards, so the pins were pointing all over the place. Probably the reason it was returned. Once that was fixed it was fine. 

I do feel like I'm behind the times though, since this is the first fully graphical/UEFI BIOS I've had. My last board had a dual view, but what could be done through the graphical view was limited compared to the trad menu system. All this memory profile malarky is new to me. I'm sure I'll get the hang of it.

 

Had the exact same experience building my current system. Things have moved on a long way since my Core i5 system from 2009! Saying that, I guess one the reasons why it seems a big change is just because of how long systems last for these days.

Rewind a chunk and it was typical to pretty much replace a PC after 3-4 years, nowadays it's not difficult to keep a system going for 8+ years with a couple of minor upgrades here and there. Hence when we do eventually do a full replacement, a lot of things have changed in the meantime.

Glad you're up and running now.

Thank you kindly. 

My heart sank a bit this morning when my Plex box was missing from the Network. It was hanging on the restart from a recent Windows update with a message that the memory had decreased "Press F1 to continue or F2 for setup". Sure enough, only 8 of 16GB showing. I pulled all the sticks out and reseated them, which restored the full amount. Hopefully that's it.

Those of you waiting on the least bit of news from me (which not even I do) will be delighted to know that I got in excess of two more years of service from the PSU mentioned in this thread. It is now totally defunct, failing paper clip and multimeter tests. Seems to have been killed by a very long run of FlowFrames, a video frame interpolation app which uses GPU, CPU, Disk and RAM intensively. It probably lasted for over two hours of this and suffered numerous similar insults in the last couple of weeks. I'll be interested to see whether it actually finished when the new PSU arrives.

Had a work NAS fail unexpectedly a few weeks back. Not a drive issue (the 4 RAID drives in it are probably fine); a 'zombie' celeron/chipset (LPC clock) issue we were never notified of. Luckily this was our formerly main file server that had been relegated to backup use several years ago ... I look at these devices differently now.

That all looks a bit complicated to me. I just bought a new PSU which should arrive tomorrow. There's a sorry looking pile of snipped-through cable ties as well. Doesn't hold the same excitement for me as building PCs used to have. I did (briefly) consider buying a PSU from a local PC shop, the kind of place where they still offer advice on how to set up your config.sys and autoexec.bat. Then I saw how much their cheapest PSU was. Sad really. 

Yeah I'm not down with smd soldering, though I did something similar -ish to convert an old radeon gpu from windows to mac (also had to reflash the bios). Surprisingly it worked, and is stuck in a G3 powermac under my desk that hasn't been booted in ~10-years. Where does the time go?

Ho Ho. Or possibly ho hum. So the new PSU went in like a charm. It's a nice quiet Gigabyte jobby, fully modular (although tbh I've never quite seen the point of having the mainboard supply cable as modular, unless you intend to have two PSUs for a load of devices, with only one mobo). 

Of course, because it was so straightforward, I had to have a poke about in things like device manager and event viewer and suchlike. 

Spotted that there'd been about half a dozen BIOS updates since mine, including some major security bits and bobs. So I stuck a new BIOS in. That worked like a dream too. 

Then I checked my email and found out that my copy of MS Office 2019 had been deactivated by the BIOS update. As the thread title expresses it, "POO!" That nice man in Slough who sold me my copy doesn't seem to be around anymore, so I'm seriously contemplating becoming legit and subscribing to Office 365. I suppose I could go Open Sauce with Libre Office.

I use both and prefer libre except sometimes it messes up the formatting of Word docs if there is some kind of elaborate layout with pictures. Other than that it transparently opens and writes valid .docx etc formats. The Excel clone is pretty usable for an amateur like me.

I've used Libre Office (and Open Office before that) for years, on and off. I briefly used it for my main office suite. Interesting differences, and mainly down to personal preference I suppose, but I always liked MS Office best. I can see why things might be the other way. It wouldn't break my heart if I was "stuck with" Libre Office.

Mind you, when I started work we had a typewriter for everyday letters, and most memos were written with a pen. 

I like LO because it's free, and also because I hate Microsoft and the horse the it rode in on.