Sign in with
Sign up | Sign in
Your question

New PSU -> Power goes on and off and on and off...

Last response: in Components
Share
October 5, 2009 9:26:24 AM

I changed the PSU of my PC in order to upgrade the GC, When I switch the system, Front power light flashes on and off, and I hear the fans starting to spin then stopping, and it goes like that until I switch the PSU off. With the original PSU, everything works. Anyone got an idea?

More about : psu power

a b ) Power supply
October 5, 2009 10:16:29 AM

If you can try and check that PSU in another PC...

I would suggest you check with this...
Even though it reads - New build, still your case is very much the same...
http://www.tomshardware.com/forum/261145-31-read-postin...

So even after these steps the problems remains, then the problems must be with that PSU...
October 5, 2009 10:57:51 AM

Thanks for your reply!!! Unfortunately I cannot test the PSU in another PC.

I saw the thread you mentionned, but several steps are ruled out by the shear fact that my systems runs perfectly fine with the old PSU.

I guess I was hoping someone would recognize that problem and give me a simple and straightforward answer to get me started as I tried everything my logic and the provided info intructed me to :-)

What bugs me is that I have the sneaking suspicion that the PSU's not at fault, that it's only just a small detail, maybe the way the power switch is connected to the MB or whatnot that's causing the issue. Sending it for repair only to get a brand new one which displays the exact same behavior in a couple weeks.... Well that'd suck ;-)

Related resources
a b ) Power supply
October 5, 2009 11:47:25 AM

^ Well if you want a straight forward answer, then it would be - Your new PSU is the problem...It should be obvious to you too...And I dont think there are any different ways of connecting PSUs...
October 5, 2009 12:02:12 PM

I didn't meant the way the PSU is connected to the MB(altough there is several options), but the case power on switch to the mainboard, but I don't feel like shunting the pins on the MB end. Oh well... might as well start the RMA thingy, and keep looking at that GeForce GTX 275 box collecting dust while I struggle to make do with that POS GT 230... *sigh*

Thanks anyway :-)
a b ) Power supply
October 5, 2009 12:31:44 PM

^ It is always very sad when you get a defective component...

And I wouldn't want to shunt the pins on the MB...Why would you want to when you are 99% sure it is the mistake of the PSU...

And Good luck with your RMA...And by the way, what PSU did you buy ?
October 5, 2009 1:22:11 PM

I bought a corsair HX750W in replacement of a noname stock 450W(370W real) PSU.
a b ) Power supply
October 6, 2009 3:47:29 AM

^ Ohh...that's an awesome PSU...And now I have certain doubts regarding the way you connected the cables to the PSU...just check with the manual once on the cables that are connected to the PSU...
October 6, 2009 7:28:10 AM

Actually the problem occurred without any of the modular cables attached, and with the old GC which didn't need external power.

Original PSU was connected to the MB trough one 24pin cable, and one 4pin cable.

I merged the 20+4 connector going out from new PSU and connected that to the MB, then splitted the 2x4 connector and plugged only one to the MB (tried with both).

No luck...
a b ) Power supply
October 6, 2009 9:02:20 AM

^ Such a bad luck to get a faulty Corsair PSU...
That's pretty rare...
a c 142 ) Power supply
October 6, 2009 2:36:22 PM

Rollmops said:
Actually the problem occurred without any of the modular cables attached, and with the old GC which didn't need external power.

Original PSU was connected to the MB trough one 24pin cable, and one 4pin cable.

I merged the 20+4 connector going out from new PSU and connected that to the MB, then splitted the 2x4 connector and plugged only one to the MB (tried with both).

No luck...


If your motherboard has a 2x4 cpu connector, you want to use both sides, even if you only used one before . It provides extra power for some configurations, and the motherboard can use it. This might be necessary to add power to the pci-e slot so that your new graphics card(what is it?) can function.

Look carefully at the modular connectors to be certain that the ends are both securely inserted, and that there are no bent parts. Try to substitute some other connectors if possible.
Do plug in the leads for your new graphics card.

Try the system using the old graphics card.

Corsair has an active support forum, open a dialog there.
October 6, 2009 3:51:46 PM

My MB has only one 4pin connector close to the CPU and PCIe bus, otherwise I'd have plugged both for sure :-) The old PSU was plugged by the 24pin connector and this 4 pin cable, and is again now, and everything works.

I made sure the connectors were not bent and cables not otherwise damaged.

The problem occurs with the old CG (GeForce GT 230 only OEM provided, with no external power connector). Not confident enough to test with the brand new GC, and won't until my system boots at the very least...

The new GC I was about to install is a Zotac GTX 275.

I opened a topic and sent a PM to some Corsair gurus, but no luck, and I can't find anything online. Well that's not exact, I digged up some old posts with similar problems, but none included any kind of answer or solution.

Tomorrow I'll bring my PSU at work and try to plug it in a desktop that sits in a corner... If same symptoms, I'll bring back the PSU to my dealer to get a refund/replacement unit.

October 7, 2009 9:54:07 AM

Update :

So I brought my PSU at work, and plugged it in a PC that was lying around. And everything runs smoothly!!!!!!! The PSU just powers the damn thing silently and without a hiccup, as expected from a Corsair part. Now I'm glad I didn't fill a RMA too soon because it'd just be a waste of my time and theirs to shuffle around a perfectly working unit.

Still, I'm stuck with my problem and have not the slightest idea what might cause it.

Is HP known to fit their Pavilion desktops with non-standards PSU and MB ??? I can't believe they strayed from standard just for the sake of it. The connector cables colors match 1:1, and I didn't make any mistake while plugging the stuff.

How can I rule out the case power on switch?
a c 142 ) Power supply
October 7, 2009 2:57:02 PM

Rollmops said:
Update :

So I brought my PSU at work, and plugged it in a PC that was lying around. And everything runs smoothly!!!!!!! The PSU just powers the damn thing silently and without a hiccup, as expected from a Corsair part. Now I'm glad I didn't fill a RMA too soon because it'd just be a waste of my time and theirs to shuffle around a perfectly working unit.

Still, I'm stuck with my problem and have not the slightest idea what might cause it.

Is HP known to fit their Pavilion desktops with non-standards PSU and MB ??? I can't believe they strayed from standard just for the sake of it. The connector cables colors match 1:1, and I didn't make any mistake while plugging the stuff.

How can I rule out the case power on switch?


I would try installing your new graphics card and plug in it's power connectors. Perhaps the motherboard is having a problem displaying the startup displays. The power on switch is a momentary contact switch. It is unlikely to be the problem since your old system works with it, and your system does try to start. You could always manualy short the two mobo pwr pins if you needed to.

Is it possible that your wall outlet is not properly grounded? A Good psu will need a proper ground.
October 8, 2009 7:32:47 AM

Yeah, might as well check if grounding is the problem by testing in another wall plug.
March 26, 2011 4:37:35 AM

Ok - thanks to this thread I fixed it. Also Corsair 750 w - cycling on and off including motherboard. Solution motherboard not getting enough poer throug the usual plug (I think 24 pin) also make sure you plug in teh other cable into the mobo that powers on graphics card. This is in addition to plugging power into the graphics card. It never needed it, then after I was trying to do something with graphics it went down and from then on would power up and then go off - over and over. After haveing evrything tested (expensive and time consuming) all it needed was some more power (the 8 pin plug into the motherboatd from the PSU). Thank goodeness for this forum - very helpful.
!