Maximus VI Hero fuse blew up on start up

[Arborescence]

Solved

[Whiskers54]

Arborecsence,

Just what you don't want to see....ever. Hopefully your place of purchase will issue you a new board and get you up and running quickly.

On a personal note, I would contact Corsair and explain your situation to them and see if you could get a different PSU. That way you would have peace of mind by eliminating a possible bad PSU and you buying another Hero if it would happen again.

[Nodens]

This is caused by bad PSU, a short or possibly faulty case header (eg USB). Also have in mind that PSU surge protection is far away from surge-proof. It's like 60% effective only. They only protect against small to medium size surges. Any big surge would burn PSU MOV and residual current WILL flow into the circuit. Do not think you're safe just cause PSU says it has Surge protection..

[Arborescence]

Thanks for the input Whiskers54 & Nodens.

A bad PSU is of course the first assumption, but I'm wondering what the purpose of the Corsair AX-series self test is, if not to rule out PSU problems? I thought it supposedly tests that the voltages etc. are good to go. Well, I've opened a ticket at Corsair tech support on this, we'll see what they have to say.

I can see that a faulty case header might cause problems too, but there's no easy way to test this... I did have all the case headers, such as USB and of course the power switch and fans attached.

Will report back if there are any developments.

[HiVizMan]

Self test simply tests if power is being delivered to the test circuit. Nothing more.

[Arborescence]

Sounds plausible, HiVizMAn, but there is contradicting information out there. The linked KitGuru review claims that:

The self test switch on the PSU confirms that all the DC output voltage rails are functioning correctly, and the fan is functional, providing a simple method of checking that the power supply is functioning correctly.

I couldn't find a similar claim from Corsair, they simply talk about PSU "functionality". So, you may be right, but if that's the case then I really have no way to know whether the PSU is good or not.

[HiVizMan]

Correct functioning normally means power is on each rail and that the output is present on each rail. There is no deeper test, as to do so would require a load being applied and that is not possible.

[Nodens]

Viz is right of course. The text you're quoting is open to interpretation heh. As in "It confirms that the test circuit (because that's what performs the test/gets the readings)receives the proper power on each rail". But that's it. And the test circuit doesn't even catch power artifacts. The only real way of checking a PSU is with an oscilloscope.

But all that have nothing to do with surges anyhow. PSUs are surge protected using MOVs (http://en.wikipedia.org/wiki/Varistor). A MOV will zero its resistance when the voltage is above the threshold the MOV is rated for. This causes power to flow into the MOV instead of the circuit. But if the surge is high enough, the MOV will burn out and won't absorb the entire surge. The rest of the power will flow into the circuit:) Residual power may flow into the circuit even if the MOV is not burnt out. That's why enterprise power installations use a series of stacked MOVs on their power grid (eg a huge MOV on the main power source and smaller ones at the power outlets that catch whatever manages to flow beyond the big MOV).

[Praz]

Below is a pic of a power supply I had that took out 2 different motherboards. When the first board quit working I measured the PSU rails and all voltages were within spec. Swapped in the second board, powered it up and it immediately shut down and never powered up again. I pulled the power supply, loaded all the rails and checked it with a scope. As you can see the DC voltage is right at 3.3V. Superimposed on the DC is a ramping AC voltage that is peaking at 2V. This is what killed the motherboards and no basic testing or DMM voltage measurements would detect this.

[Classic_GOD]

Praz wrote:
Below is a pic of a power supply I had that took out 2 different motherboards. When the first board quit working I measured the PSU rails and all voltages were within spec. Swapped in the second board, powered it up and it immediately shut down and never powered up again. I pulled the power supply, loaded all the rails and checked it with a scope. As you can see the DC voltage is right at 3.3V. Superimposed on the DC is a ramping AC voltage that is peaking at 2V. This is what killed the motherboards and no basic testing or DMM voltage measurements would detect this.

So true. I've seen countless examples where a friend or coworker that know a little more about computer bring a unstable/broken PC to me saying "It's not the PSU, the voltages are OK." and first thing you see afterprobing it with an oscilloscope is the ripple larger than the waves in 'Perfect Storm' 😄
I even had an idea of getting one of those DIY micro oscilloscopes with OLED screens and putting them in the case with 24pin, 8pin etc connectors to test PSU's in the field but I'm not sure if resolution on those micro oscilloscopes is sufficient.