New PSU, Immediate Shutdown. (Solved)

[ElT]

Seeking some help.

I've just bought a Seasonic Focus Platinum 850w to replace my old PSU. The old PSU was working but it only had one 8-pin CPU/Motherboard power cable (built in) and my current motherboard has two sockets. I was running it okay with just one of them supplied but when the graphics card (a very thirsty Radeon 480) really ramped up, I'd get a black screen and a crash, which I guessed to be me exceeding the power supplied to the motherboard. So - new PSU.

Everything is connected up. I flip the PSU switch from O to I and the power light appears on the motherboard. I then press the power switch and the PSU spins its fan and it looks like everything is about to start for approx. 0.5seconds. And then the illuminated logo on my GPU comes on followed by immediate shut-down of the PSU. Pressing the power switch will no longer have any effect until I've completely cut off power and let the motherboard lights fade off at which point I can repeat the whole process. Am guessing this last part is some safety feature of the motherboard or perhaps that it still thinks it's on in some way.

I've tried with both 8pin CPU power connectors attached, and with only one which is how things were with the old PSU. I've actually re-connected the old PSU and everything is working fine again (big relief).

The Radeon 480 takes a single 8-pin PCI-E connector and that was connected. A single SATA power cable is as well. The PSU has a good reputation and is new, so is there anything I can try or any stupid mistake I might have made before I send this back?

Any help welcome. Patronisingly stupid things I might have done also welcome.

Thanks!


The PSU:
https://www.overclockers.co.uk/seas...-platinum-modular-power-supply-ca-05w-ss.html

The motherboard:
https://www.overclockers.co.uk/msi-...9-socket-tr4-e-atx-motherboard-mb-33x-ms.html

 

[ElT]

I think so. It's one of the things I was very paranoid about getting wrong because I know that if you connected PCI-E to the 8-pin CPU power socket you could destroy the processor. And the PSU has double-purpose PCI-E/CPU sockets so this was a real concern. But so far as I can see the sockets are keyed to not allow a mistake. The cables have "CPU" in white text on one end and "PSU" on the other and those I placed into the PCI-E/CPU socket on the PSU and motherboard on the other. The one into the graphics card goes into the same sort of socket on the PSU but has PCI-E written on it. I didn't try them in multiple sockets on the PSU.

 

[ElT]

You are using the cables that came with the new psu and not using the old psu's cables?

I've used the cables that came with the new PSU for the motherboard and PCI-E connections. For the hard drives (I have 6 SATA, plus 3 M.2 on the motherboard itself), I used the existing power cables as I assumed those ones were the same. I did try it without those connected at all (my boot drive is an M.2 on the motherboard) and it didn't seem to make a difference.

 

[ElT]

I've used the cables that came with the new PSU for the motherboard and PCI-E connections. For the hard drives (I have 6 SATA, plus 3 M.2 on the motherboard itself), I used the existing power cables as I assumed those ones were the same. I did try it without those connected at all (my boot drive is an M.2 on the motherboard) and it didn't seem to make a difference.

It's not a Vega card but this sounds very much like what I'm experiencing. The speed at which it shuts down and the point at which it does it (GPU comes on, everything shuts down) feels very much like some safety cut-off coming on. The article says Seasonic changed the trigger level for the cut-off in later versions but there's no reason to suppose I have a later one just because I bought it recently. Maybe there's something on the labels but they're all on the underside of the PSU so I'll wait till I take it out again to check. Probably no definite confirmation on there, anyway. So I guess two ways to test this would be to remove the graphics card entirely and see if I get the no graphics card found beeps. Obviously that's not a solution but it will hint that this is the problem. Other would be to swap in an old GPU. I think I have a... Radeon 280 lying around? No idea how much power that draws. Hopefully less.

I think there's a good chance you might have found the issue because while your link talks about Vega, the 480s had a big reputation for power-gobbling. Including drawing more than they were supposed to from the PCI-E slot. My old motherboard could handle it but that was an FX-8350 with a dribble of RAM and a little fan. This has a Threadripper, 64GB 3200 RAM, multiple M.2 SSDs, multiple external fans... It can't afford to have the GPU mooch off it anymore which is the what instigated the new PSU in the first place. But all my calculations say 850W is more than enough for the system. So really disappointed in Seasonic if this is the case.

Thanks for the link. Will test out the hypothesis after work.

(btw, old PSU was 750W Corsair Hx so this should be an upgrade).

 

[ElT]

I have both the 850 prime platinum and also the 860 Platinum (not prime but the other one) and a TR 1950x, 64GB of 3466 and radeon 7 + vega64 and mine have never done this. 860 is more than enough for your system, possibly slightly on the edge for mine but still never experienced this... Stupid question but is the 24 pin, 8 pin and 4 pin all plugged into the board snug.. (might be different connectors on your board to my Taichi)

Good to know. I too am pretty sure the PSU should be able to handle it. The problem was specifically with their Focus line according to the article. Finishing work shortly so will try without the graphics card and maybe that will shed some light.

I would also check the 8 pin to the gpu and just make sure its properly snug at the gpu end. fwiw I ran a 480 in mine before I had Vega and the 480 sips power in comparison.

I believe they were. But I'll double check when I swap the PSU back in.

Never interchange PSU cables from one PSU to another unless you know for certain the pinouts are identical.

Even PSUs from the same brand can have different cables from one PSU model to another.

Even the SATA power cables? I'll swap them over then. I just didn't because I had the old ones nicely all tied in place.​

 

[ElT]

Sorry to tell you this but you may have fried something by using cables that are not intended for use with that psu. All it takes is one wire in the wrong place. Never, ever use the cables from one psu with another unless it's exactly the same unit or you have made extremely sure that the wires are all in exactly the same places. This may have been a very expensive lesson to learn.

Computer and all systems are working fine with the old PSU back in place. But point taken for any future operations - thanks.

 

[ElT]

We have winners - PastyMuncher and an0nym0us. I'm currently typing this from a fully operational Deathstar PC. So the SATA powercables are different between my old PSU and the new one. And yes - I'm very grateful I didn't damage anything. The old ones are like this:
(Clip at the top, R = Round, S = Square. E = Empty / No pin socket)

R S S
S E R

The new ones are like this:

E S S
S R E

I had honestly thought that Sata-PSU cables were standard. The old ones fit because the pin casing shapes are the same but as you can see above, some of them are empty in one but not in the other.

Big thanks for all replies. Saved me sending back a working (so far) PSU. Very quiet as well.

Now to decide whether to get a 5700 GPU whilst I'm rebuilding things... /tempted