PC won't turn on

Mr Cochese · 1 Mar 2019 at 13:10

My under TV PC just turned off mid-game the other night and won't turn back on when the power button is pressed. It's an Overclockers bundle from four years back called the "ForceBox Genesis X2", so i didn't build it myself and aren't even sure exactly what model the motherboard is, but the PSU is a Silverstone SST-ST45SF.

I've got the box stripped down to just the PSU, Motherboard (with memory) and front panel. There's a green light on the motherboard when the power is on, so clearly something is getting through. When I've not tried the power button for a while and press it, the CPU fan briefly spins before giving up, and the front panel power LED also flashes, but other times there's nothing. The fan on the PSU is not moving at all, but hard to tell if that's just because it only comes on when needed. I've tried reseating all the power connectors I can see, and the CMOS battery, so I gather this means I probably either need to replace the power unit or the motherboard?

Sorry, I know there's the sticky thread on this sort of thing, but it sounds like this can be hard to diagnose and I don't have much equipment to hand, so grateful if anyone can suggest anything.

EsaT · 1 Mar 2019 at 15:56

Model of motherboard reads on it, likely between or above PCI-e sots.
Also does it even POST to BIOS with minimal parts?
(no HDD/SSD, integrated graphics card if possible and only one DIMM)

Anyway if that's whole model designation (no G in end) that PSU isn't good for cramped cases with not much of cooling.
Secondary is full of cheap capacitors.
https://www.pcper.com/reviews/Cases-and-Cooling/SilverStone-ST45SF-G-450W-SFX-Form-Factor-PSU-Review
https://www.chiphell.com/article-3954-4.html
In that first one Silverstone wasn't even interested on complying with ATX specification. (SFX uses ATX standard except for physical size)
Allowed max ripple is 50mV for 3,3 and 5V and 120mV for 12V...
So Silverstone saying that they don't guarantee better than 70mV and 140mV is fishy...

Mr Cochese · 1 Mar 2019 at 18:33

Thanks. I found that the motherboard is this: https://www.asus.com/Motherboards/H81IPLUS/, which I would have known if I hadn't thrown out the box last year!

I've not been able to get POST to happen at all, and have been down to just one DIMM as you suggest. You're right about the PSU not being the -G designation - it's rated 80 Plus Bronze - so I'll definitely look to upgrade if it is indeed the PSU that needs replacing. Am I just going to have to try to test the PSU for power to figure out whether it's that or the motherboard that is fried?

EsaT · 1 Mar 2019 at 20:45

Cheap capacitor PSUs aren't anyway made to last lots of years if used heavily.
And cramped SFX form factor certainly makes internal temperatures higher.

Though also that motherboard has likely quite weak CPU VRM if you have higher end CPU.
Some small SFX possibly having weaker cooling would further stress it.

Danny75 · 1 Mar 2019 at 21:40

Maybe remove the front panel connectors to rule out faulty switch as well. Just to scratch it off the checklist. Might have fried when the system shut down mid-game. Start it up by jumping the two "PWR" positive and negative pins with a flat tip screwdriver.

Presumably it had a graphics card in when it shut down mid-game? Quite likely that died and has affected something else. Hope I'm wrong.

Tell you a story about the Asus H81-Plus and a cheap PSU - had a GTX 970 that died mid-game, system shut off. Wouldn't restart at all. I tested the card in another system with a H81-Plus and a cheap PSU, and they allowed the system to start up and then smoke started coming out of the GPU. In my own system with better mobo and PSU (that are still going strong) they recognized something was wrong and wouldn't allow startup with the GPU installed. Better safety measures/protections.

Mr Cochese · 2 Mar 2019 at 16:12

Have done the paperclip test as well now and there's absolutely no sign of life from the PSU fan, so assuming the unit is blown. If I go for the ST45FS-G, is that a much better unit for a compact system, or are there safer options?

The GPU is a GTX970, so a little old now, but happy to keep it going a bit longer if it's ok. Didn't get any smoke or burning smell when the system went down, so hopefully it's ok, though a bit alarmed by your story Danny75.

EsaT · 3 Mar 2019 at 09:58

ST45FS-G certainly has higher quality components than those older models.
Though it has just three year warranty:
https://www.silverstonetek.com/warranty.php?area=en
(with Silverstone's "best" having short five year warranty)

If PSU's length isn't that strictly limited Seasonic would have 12cm fan cooled Focus SGX with their usual 10 year warranty.
https://www.overclockers.co.uk/search?sSearch=focus+sgx
Length is just 125mm instead of 100mm.
So would have to check, if case can fit that amount longer PSU.

Mr Cochese · 8 Mar 2019 at 11:27

Just to let you all know, I put in a SF450 platinum (which seems to have reviewed really well) and everything's good. Only downside of the new PSU is that the modular cables are pretty chunky and the mains connector is the wrong way up, but I should be able to pack it all into the case with some careful cable management. Thanks for all the help and advice.

Danny75 · 8 Mar 2019 at 13:40

Glad the GPU survived after all. Which case is it all in?