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Power on

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July 25, 2010 5:47:57 PM

I have a cosmos case, asus p6t deluxe 2 MB, 6GB dominator ram, core i7 920 cpu, radeon 5870 video card, ocz 1010 psu. Just recently when i press the power on button nothing happens. It will however work if i turn off the psu wait a few seconds and turn it back on. Then everything is fine. All parts are less than a year old

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a b ) Power supply
July 25, 2010 6:55:41 PM

Have you tried replacing the PSU?
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July 26, 2010 6:37:37 PM

enzo matrix said:
Have you tried replacing the PSU?


I am hoping to get some advice on possible test procedures to determine the problem before i start throwing parts and money at it. Like i stated the hole system is less than a year old. In fact they are 8 months old. The PSU is my guess but I find it wierd that everything works fine for 5-6hr gaming sessions until I try and turn it on the next day. Also there is no electrical burning smell, sparks, or anything else to indicate it is in fact the PSU. All of the obvious things have been checked. Oh also I opened the case and the power button and reset button lights on the Mobo are on. The power output is obviously fine, it's the power up circuit that must have an issue.
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a b ) Power supply
July 26, 2010 8:12:31 PM

I have had similar behavior on my machine at random times, and I think it goes back to a confused loop in BIOS. First I'll describe my situation, then talk about what you could try.

On occasion my machine has failed to start up when I push the front panel button. But if I unplug the power cord OR just turn off the power switch on the back of the PSU and leave it without power for at least a minute (I assume in that time the PSU's internal capacitors are discharging to nothing), then restore power and push the front panel button again, it works just fine. The problem does not repeat immediately (unlike yours). My hypothesis is that, for reasons unknown, the BIOS somehow gets a little confused during a shut-down. When the computer is "Off" it is not completely off. A small loop in the BIOS is running checking for the power button push to initiate a re-start of the whole system. But I think sometimes that little monitoring loop gets stuck and fails to see and respond to the front button push. A full cold reset resolves that confusion.

Now, to your case. It is very similar to mine, except that yours happens on virtually every shut-down. I suggest a BIOS reset which takes several steps. BUT the very first thing is to record what you have. The Reset procedure will put all-good settings into your BIOS, but will lose any special custom settings you have made before, so you'll need to restore them manually. So, get pencil and paper and go thorough your entire BIOS Setup screens, writing down all the places where you have made any custom settings and the values there. Things like which drive ports are Enabled or Disabled, what SATA Port Mode settings you have (IDE Emulation, AHCI, or RAID) what Boot Priority Sequence you have, whether you changed any CPU timing or voltage settings, any custom RAM settings like voltages or timing parameters, how the audio port output is set up, what type of video output you have... all that stuff. Once you have a record of all of this you can start the Reset. Oh, just before you do: did any of those custom settings look odd to you? Maybe something you never changed, but it seems like a strange setting that might be linked to your problem? Make a note of that in case you want to try changing it later.

Before going further, consider the possibility that the BIOS battery has gone dead and needs replacement. You could just go buy a new one and do the replacement. OR, when you get the old one removed, you could run to the store and have them check it before spending money - you might NOT have a dead one there.

OK, now we do the reset, in these steps:
1. Disconnect all power to the machine. Open up and remove the BIOS battery - looks like a quarter - from its plastic holder on the mobo. (See note above about possible replacement.)
2. Find the BIOS Reset pin set - three pins with a jumper on the first two. Move the jumper to the middle and last and leave there for about 10 seconds. Return the jumper to its original location. Now replace the BIOS battery in its holder.
3. Close up the case, reconnect power. Boot up but go immediately into BIOS Setup. Look on the last couple of tabs for the place where you can load up pre-defined sets of BIOS parameters. Load either the Factory Default set or the Optional Default set. Save and Exit from this to save the settings. This procedure ensures that the BIOS is reset AND has all good parameters to start from.
4. Now reboot into BIOS Setup again and go back through all the screens. From your notes, re-set any of the custom settings you needed so that your machine is back to "normal".

This MAY solve your problem IF the cause simply was some odd BIOS setting. BUT if the problem persists you'll have to look elsewhere.

By the way, I said my computer had similar problems but rarely and randomly, not repeated. More recently and with a different set of symptoms that got progressively worse over the space of a couple of weeks, I confirmed that the PSU had failed and replaced it. I have no idea whether that eventually-clear problem was related to the earlier random failures to boot properly.
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a b ) Power supply
July 26, 2010 8:43:09 PM

jasongagne said:
I am hoping to get some advice on possible test procedures to determine the problem before i start throwing parts and money at it.

Not money. Just parts. Ask your friends to borrow their PSU. Unless you have a multimeter for basic testing, then expensive equipment for more extensive testing, the fastest way to find out what is bad in a computer is to swap each suspected part out one at a time.
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a b ) Power supply
July 26, 2010 9:12:59 PM

I've heard some of these boards need to have the cmos chip pressed down on to help seat them in the socket better while others need a new cmos battery.
Pressing down on the cmos chip is free and a new battery is cheap.

After you have tried those:
disconnect the reset sw from the motherboard.

use a pair of small needlenose plier or a piece or wire or a paperclip ... and briefly jumper across the terminals of the power sw connector on your motherboard. If it powers up there is something going on with the switch on your case.

if it didnt power up now move the jumper to the "power supply on" line of the big 20 or 24 pin connector and jumper it to ground. Its pin 14, the lone green one in the midst of a few black ones. Jumper this to ground, one of the black wires right next to it, and leave it jumpered to turn on the power supply. If it doesnt turn on you need a new power supply.

if it powers up now, repeat just his portion of the test the next time it wont turn on. If it still powers up ok then the issue is with your motherboard and I'd look for bios updates first.

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a b ) Power supply
July 26, 2010 10:14:32 PM

why did you get a 1000w psu? a 650w could have done that?
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a c 144 ) Power supply
July 28, 2010 8:14:30 PM

Paperdoc, Enzo: The problem is likely to be caused by a fault in the part of the PSU known as the standby power supply. A DMM might or might not detect the problem.

Use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

Monitor the violet wire. As long as the PSU is plugged into the wall and the PSU is turned on, you should have 5 volts all of the time regardless of the state of the case switch. You probably do have that present all the time. If you detect a voltage drop when you press the case switch (you shouldn't), you've found the problem.

The standby power supply feeds the circuits that monitor the case power switch and the circuits that generate the PowerGood control line that you need to boot.

Monitor the green line (case power switch). It should be at 5 volts. When you press the case switch momentarily, it should drop to 0 volts, and return to 5 volts. When you power down by Windows, it should stay at 5 volts, ready for the next time. Monitor the line as you power up the next day. It should be at 5 volts before you do anything.

Monitor the gray wire (the PwrGd signal). With the case switch off, it should be at 0 volts. Press the case power switch. It should quickly (within .5 secs) rise to 5 volts after the PSU voltages stabilize. Power down with Windows and it should drop to 0 volts. Monitor the line as you power up the next day. It should rise to 5 volts. When this signal goes high, it removes a hardware reset from the CPU permitting it to boot.

Although not a certainty, you have a pretty good chance of finding something wrong.
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a b ) Power supply
July 29, 2010 1:41:23 AM

Excellent info, jsc. Thanks!
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July 31, 2010 1:17:33 AM

Thanks for all the help everyone. I will get to testing your suggestions asap.
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!