Boot Up Problems

[Joker1]

A friend of mine is having some problems with his system. It's a Abit KT7A Raid running a Athlon 850 with a Leadtek Geforce 2 and a 300W AMD approved power supply. I can get more details if they help.

The system runs great otherwise. The only problem is on a cold boot. If the system is shutdown and the power button is hit then about half the time it will seem to power up for about 1/2 or 1/4 of a second then nothing.

Turning the atx power supply off and on and hitting power several times will eventually get it to power up. But why the hell does it do this? Any ideas guys? We've eliminated the power switch. Could it be the video?, Power supply? Mainboard?

[Darren Wilson]

Sounds like a PSU issue to me. Try another PSU if possible that you know works 100%. Maybe try your own in it?

[condor]

I've seen it happen many times..

it is usually PSU related..
but I would still check BIOS settings (Pwoer Management), that the CPU fan is connected to the right Power socket...

also try a CMOS reset..

[Mr_Miyagi]

beware of cpu heat damage....

(this was the result of a similar case i had -- the cpu had been partially fried and would intermitently not boot similar to your case)

imho

[Joker1]

Originally posted by Mr Myagi:
beware of cpu heat damage....

(this was the result of a similar case i had -- the cpu had been partially fried and would intermitently not boot similar to your case)

imho

I'm gonna try the different psu and the bios reset if that doesn't work. I doubt it is the cpu though since its brand new and it has a proper heat sink and fan and with arctic silver, it runs nice and cool.

[TangleWeb]

Sounds like the "latching circuit" in the PSU, as indicated by other posters. If the voltage is not up to par & stable within a split second of you hitting the switch, the "power good" signal is not sent & the system does not power on. I've had this a couple of times.

The advice to try another power supply is good. I keep an extra one on hand for just this reason. Another idea suggested by a recent poster in this forum is an ATX Power Supply Tester from PC Power & Cooling. It's only $8.00 + Shipping! What a great little tester at a great price! If it's good, you get a green light. It also puts a load on the power supply as powering it up without a load can damage the PSU.
http://www.pcpowercooling.com/products/alarmandaccesories/accessories/popups/inde x_tester.htm

Here's a description of the Power Good Signal;

"Power Good Signal

When the power supply first starts up, it takes some time for the components to get "up to speed" and start generating the proper DC voltages that the computer needs to operate. Before this time, if the computer were allowed to try to boot up, strange results could occur since the power might not be at the right voltage. It can take a half-second or longer for the power to stabilize, and this is an eternity to a processor that can run half a billion instructions per second! To prevent the computer from starting up prematurely, the power supply puts out a signal to the motherboard called "Power Good" (or "PowerGood", or "Power OK", or "PWR OK" and so on) after it completes its internal tests and determines that the power is ready for use. Until this signal is sent, the motherboard will refuse to start up the computer.

In addition, the power supply will turn off the Power Good signal if a power surge or glitch causes it to malfunction. It will then turn the signal back on when the power is OK again, which will reset the computer. If you've ever had a brownout where the lights flicker off for a split-second and the computer seems to keep running but resets itself, that's probably what happened. Sometimes a power supply may shut down and seem "blown" after a power problem but will reset itself if the power is turned off for 15 seconds and then turned back on.

The nominal voltage of the Power Good signal is +5 V, but in practice the allowable range is usually up to a full volt above or below that value. All power supplies will generate the Power Good signal, and most will specify the typical time until it is asserted. Some extremely el-cheapo power supplies may "fake" the Power Good signal by just tying it to another +5 V line. Such a system essentially has no Power Good functionality and will cause the motherboard to try to start the system before the power has fully stabilized. Needless to say, this type of power supply is to be avoided. Unfortunately, you cannot tell if your power supply is "faking" things unless you have test equipment. Fortunately, if you buy anything but the lowest-quality supplies you don't really need to worry about this."