PSU OK with Celeron, not with Broadwell - likely?

[Giraffe]

My ongoing saga with a Z97 mobo and Broadwell CPU: twice to Gigabyte's repair facility (only 10 miles away) has resulted in a possible problem with the PSU.
On the bench, either CPU would run with the lashed in PSU - but that was about 750W.
In the case at home, Broadwell still won't run.
The tech. chap suggested that the PSU hadn't enough power for the Broadwell, so...

PSU is http://www.scan.co.uk/products/450w-...mm-fan-atx-psu
running only 3 fans and a 2.5" Travelstar HDD - hardly a big load!

On the Celeron, the power in to the PSU peaks at about 38 - 40W and is about 28W idling.
On the Broadwell, which doesn't boot but goes for about 20s, the power is pretty well the same.
As the PSU is rated at 40A on the 12V rail and is 12.13V off-load, it would seem that the PSU being at fault is unlikely.

Any other ideas, please?

[Splash]

Works with a different PSU, but not yours? Looks fairly cut and dry to me. Of course, this could mean that you have a faulty PSU, rather than it just being unable to supply the juice needed by design - I'd expect 450W of decent PSU to be more than up to a CPU, some RAM, 3 fans and a hard disk (you don't mention GPU - is this onboard?)

[EndlessWaves]

Yeah, it's not a capacity problem. You don't say which CPUs are involved but the 5675C/5775C are unusually low power CPUs due to their low clockspeed. They're probably a few watts more than the similarly clocked haswell celeron but I'd be surprised if the system ever pulled 150W, let along anything close to 450W.

I take it you managed to get your GA-Z97-D3H rev. 1.1 flashed to the latest BIOS? Have you tried resetting the BIOS to default settings and then swapping in the 5675C?

[Giraffe]

There's no separate graphics card - for what I want the integrated one is more than enough (the nearly 9 year old Radeon 1250 does the job, but wouldn't drive the 1920x1200 monitor).

I did flash the BIOS to F9; the only original change was from instant-off to a few seconds delay on the Power switch - don't want inadvertent finger trouble!.

I'll reset the BIOS anyway and have another go. Also try to get a voltage reading of the 12V on-load during boot. There might be something limiting the current that doesn't show up on a DMM - where's an AVO 8 when it's needed!

[mortispriest]

Any psu is = but use separate graphic card or what? 450w is good
not good whit graphic card
buy only psu 80PLUS good duration and modulation sistem

[DanceswithUnix]

If the PSU thinks it is doing a poor job of controlling the voltage (say the 12V line is heading towards becoming a 13V line) then it should shut down, so perhaps that is what it happening. It isn't just about total power it can produce, it has to regulate well when load is coming and going quickly.

You may even find that adding extra load like a graphics card makes the job of the PSU easier.

Perhaps the board and the PSU just don't like each other.

[Giraffe]

I might try using the PSU from this PC. It's 330W Seasonic, so lower power but has been good for a long time.
Trouble is, if a good quality PSU is the problem, what the hell do I do - could get expensive, trying PSUs!

[DanceswithUnix]

If that works, you could just try a swap

[Giraffe]

Checked all the voltages on-load. All within spec. and +12V is 12.14V, so that should be no trouble.
Haven't yet swapped PSUs as I'm on the cusp of changing ISPs, so don't want to be off-line when that happens.

[AzumaKazuma]

Are you sure you're connecting the PSU to the mobo correctly? Including the extra 12v 4 pin connector for the CPU?

[Giraffe]

Yes - it is supplied already joined to the 20-pin.
Also, both the other 4-pin plugs are on - they're joined together anyway.

[Giraffe]

Just tried the 330W Seasonic - no luck