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PSU slow to provide power, I think !!!!


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I have an AX850 PSU providing power to an ASUS P8P67 Pro v3 motherboard. My CPU is an Intel i7 930 @3.4Mhz and a ASUS Matrix GTX580 provides the graphics.


A strange problem has developed over the last few days. When I turn on the mains supply to my system both the monitors turn on and so does my printer and external

speakers however when I turn the computer on nothing happens. Only after 30 to 60 seconds when I again try to turn on the computer will it start. It acts like the old

radios that used tubes; they needed to warm up first before the radio would work.


Due to a road accident I can no longer maintain my system and need to get in a technician to do any work, at a fee or course. So I am asking for help from anyone who

may have heard of this so at least I can pin the problem on a component before calling in the tech.


Any help would be much appreciated.



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All the items are plugged into an 8 socket surge protector and that is plugged into the wall socket. To check that the surge

protector was not at fault I just plugged the computer into the wall socket which resulted in the same problem.


I am not sure this is normal as in the past I have been able to turn on the wall socket and strait away turn on the

computer without this annoying delay.


Something somewhere has developed a fault, but what!!

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It just started a day or so ago ... I have been running stable with my current system for the last 2 months.
A power supply could have been defective 2 months ago. And is just starting to cause failures. The defect would have been seen 2 months ago with numbers from a meter. And can only be identified now if you provide those numbers.


A power system is more than a power supply. The requested numbers means you are telling better educated what all power 'system' components are doing. But only if you disconnect or remove nothing.


Borrow one tool. Or buy it even in Kmart - because its intended users are even 14 year olds. A multimeter is in Harbor Freight for $7 or $17 in Walmart. Also sold in most any store also that sells hammers.


Set a multimeter to 20 VDC scale. Connect its black lead to the chassis. Find a purple wire that connects the power supply at the motherboard. Touch the red probe to that wire inside its nylon connector. Read about 5 volts (even when a computer is off). All three digits are reporting significant information. Report that number here.


Do same for a green and a gray wire both before and as the power switch is pressed. Report those numbers and behavior. And finally report behavior and final number from any one red, orange, and yellow wire when the power switch is pressed.


A power controller determines when a computer powers on and off. Your strange behavior somehow involves that controller. What that controller is doing can only be seen with a meter. Either report those numbers to have an answer without wild speculation. Or just keep replacing good parts until something works. Those are your only two choices.


Only way to get a reply from those who better know this stuff is numbers from a multimeter. Your replies will only be as useful as facts (especially numbers) that you first provide.


Doing the above procedure means you have a conclusive answer immediately. Any layman can make those measurements.

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Thanks for your input.


Having broken my back in a road accident I only have the use

of one arm. Doing what you ask is not really possible.


In a perfect world I agree getting those measurements would be

a good idea and is something a tech. I will have to employ will

no doubt do.


I was just hoping that someone may have had a similar problem

and could point me in the right direction as to what the problem

might be. I wanted to cut down the length of time the tech was

on site as he charges fifty UK pounds per hour!!!


I give it a few more days to see if anyone else reply's before I

call in help.

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In a perfect world I agree getting those measurements would be a good idea and is something a tech. I will have to employ will no doubt do.
Most computer techs do not know how electricity works. No electrical knowledge is required to pass an A+ Certified Computer Tech exam. Most techs just shotgun - swap parts until something works. Most techs assume only a power supply is the entire power system; do not even know about a power controller. Information that can better identify a minority - the fewer educated techs.


If you find a tech who knows how to use a meter, then don't ever let him get away. Many falsely assume a motherboard monitor (the BIOS) can provide those numbers. Three digit numbers from all six wires (as described using a multimeter) provides information necessary for analysis of everything.


Nothing posted says what you should look for on that meter. Those numbers contain too much information to post here. But posting those numbers means a reply says what is and is not working - without speculation. This post describes how to locate a rare tech who actually knows how a computer works. And how to use those numbers to actually have a useful reply.


Either power is good which permits the CPU to execute in less than a second. Or a controller shuts off power immediately. That simple as peanutz94 also noted. If you want a solution, then numbers are required. Or keep replacing good parts until something works.

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Your problem is most likely the power supply, although there is a small possibility it is the mother board.


A simple test for you that should give you more insight into your problem is the following, if you can get the PC and yourself situated appropriately to do this (referring to your difficulties from the accident, sorry about that):


I'm sure your mother board has a power LED on it, sometimes referred to as the Standby LED, that will remain on when the PS is on and connected to power. Since you control power through an outlet strip, when it's switch is off, the boards LED is off.


If you can see the boards LED somehow, through the top or side of the PC case, or with the side removed, keep an eye on it while you turn on the power from the power strip. Modern power supplies like yours will have a very slight delay before being fully on, due to the automatic line voltage and frequency sensing circuitry sorting things out, but not more than one or two seconds. A few seconds after turning on the power strip, the mother board's LED should be on.


If you happen to use a separate network (NIC) card installed in a PCI slot, they have indicator LEDs that come on when the PS is on, even if the PC is shutdown. That's just another method of seeing if the PS is supplying power to the board when the PC is off.


If the mother board LED does not come on quickly, that points to the PS being at fault. If the board LED does come on quickly, but the PC won't start, that indicates something else is not right.


You did not mention whether or not your PC functions normally after the 30 to 60 second failure to start interval. You could also check the voltage readings in the BIOS, to check if they are out of spec, another quick and dirty PS test.


Any PC technician will attach their little PS testing unit to the 24 pin mother board cable, and read the answer it provides, good or bad. They may go a little farther than that with other cables, but that's it. If they decide the PS is bad, they'll replace it and if that does not fix things, they'll go from there. Not the best way of doing things, but that's the way it is done in our, hurry up, is it done yet, next customer, culture.


Good luck with that PC and let us know anything else that you can.


I have an AX850 PSU providing power to an ASUS P8P67 Pro v3 motherboard. My CPU is an Intel i7 930 @3.4Mhz and...




Just a FYI, a P8P67 is a socket 1155 board, for Sandy Bridge CPUs, while an i7-930 is a socket 1366, first generation i-series CPU, which are incompatible. No doubt just a typo.

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Wow lots of help.....


Looks like I will have to bite the bullet and get a tech in. She is normally quite good and seems to know what she is doing.


To your question parsec, yes when it does start it runs perfectly and congratulations you win the spot the mistake comp.

NO prize though I am afraid. I do in fact have a Intel Core i7-2600K running at 4.3GHz. Seems my memory is going!!!


Thanks for all your help guys.

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No prize?! Perhaps I win the flaky power supply? ;): Ah yes, that vacuum tube rectification takes time to come up... can you imagine...


Pure speculation, but a slow to start PS could be a bad capacitor that takes time to become charged up, or a poor connection to the capacitor. Also a bad rectifier or diode that does not like being cold and wakes up once warmed a bit could cause your issue.


One "solution" to your problem would be keeping that PS connected to power all the time. But it likely has a bad part somewhere, so replacing it sooner than later may be your best bet. Good luck.

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Im facing the same problem :( (I have an ax850 too)

When turning the power on at the plug it can take up to two minutes for the lights to come on the motherboard (sometimes its instant).

Ive noticed that this usually occurs on cold mornings.

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Sam, sorry about your issue but glad you mentioned the mother board LED. What other simple way of checking that the board has power besides that LED is there, besides turning the PC on?


The delay of power from the PS is curious, and that it may be related to temperature. But otherwise your PC runs fine? Have you ever checked the voltages in the BIOS or via program, and do they seem fine? Is it correct to say that the PC won't start until the mother board LED is on?

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During this period (waiting for the mobo led to come on) the power button does nothing.

After a while you hear a click from the psu and then all the led's come on and you can start it as normal. The computer is completely stable once its on and all the voltages seem normal.



Its just some mornings it takes up to two minutes for the mobo led to light up after you turn the pc on from the plug which is quite annoying :(

And I have a feeling its going to get worse as winter approaches.

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The computer is completely stable once its on and all the voltages seem normal.
Normal is for a defective supply to boot a computer. That computer can work for months. Then suddenly do strange things. That defect can only be identified months earlier with a multimeter.


BIOS numbers are also insufficient information. That 'multimeter on a motherboard' is often uncalibrated. Is only a monitor. But it can be calibrated by using a multimeter. Again, that simple tool is important.


Too often, many say voltages are good. Then when the actual numbers are posted, a voltage is discovered defective. Another example of why useful conclusions must include the numbers.

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  • 1 month later...

Hi - this is just an update,


I kept the psu for a little while hoping to replace it after Holidays. Unfortunately the problem became worse very quickly. It started to take around 30 mins to 1 hour for it supply power to the motherboard after being switched on at the wall. Then it wouldn't turn on at all.

I have now sent the psu back and got a replacement and everything is working as it should. I was very happy with the turn around speed / service I got from Corsair.


However I have 1 issue which has been mentioned a few times before and thats postage costs.

It cost me just under £30 (€36) to send the psu from the UK to the Netherlands :sigh!:

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I have now sent the psu back and got a replacement and everything is working as it should.
As with the OP, your supply was probably defective months ago. Normal is for a defective supply to still boot a computer. A defect that only gets worse with age. And a defect that could have been identified in the beginning with numbers from a multimeter, as described previously.


Learn from the original failure. A meter is a first tool on a new PSU when first powered. Numbers will report on things you did not even know existed. Report numbers so that others who better know this stuff can demonstrate how to avert future failures. And how to identify a defective new PSU before the warranty expires.

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