Weird power supply issue?

[ik9000]

Help! What on earth is causing this:

I just built a new system from scratch, all new components. Powered it on last night. Everything works as it should. Except that when you first power it up something makes a weird sound (ends after 30s or so) and all the lights in the room start to flicker, like disco-strobe (they are LED dimmer bulbs). Once the machine is running everything is fine. A restart doesn't cause the issue, just cold-start from powered off. Sometimes I have to manually adjust the light dimmer to get things stable again. WTF is happening?

Is it EMI? Is it a case of too little load on the PSU? Do I need to throw some old HDD in there to boost the start-up load? Is it interference from the surge protector? I'm loathe to plug it in without the SP as 1) it is the extension cable to get power to the desk, and 2) it just feels unwise, I've never run my desktop without one - and I've seen other people have screens go pop due to bad rental wiring etc, though that shouldn't be an issue for me I would hope as the house is newly wired in the last 12months to modern regs with MCBOs on the mainboard etc. Lights and plugs do not share a circuit at all.

PSU is a brand new Seasonic Snowsilent Titanium Prime Ultra 750w SST-750TR. Surge protector is a belkin unit like this:

[IAmATeaf]

Does it do the same when plugged into another socket in the same room or even a different room. Just wondering if it might be a socket or circuit problem.

[ik9000]

Shouldn't be but I will check to make sure.

Nothing else has had issues and the wiring is modern, however as with all oddities - rule out the simple things first. I will do a lot of such testing when I get home this eve.

[VersuS]

I'd contact Seasonic, better safe than sorry if it's a new build.

[ik9000]

fairly certain it was the surge protect. Gone straight into the wall and everything's fine.

[adidan]

fairly certain it was the surge protect. Gone straight into the wall and everything's fine.

Was going to suggest.

My electricity started tripping out whenever I put the pc on for anywhere between 5 and 20 or so minutes.

Swapped out the surge protect and no more tripping.