[adriane28]

Hello all and thanks for any help... My computer is less than two years old. When I attempt to boot the computer goes to the POST/BIOS login screen then freezes. When I restart the system, it attempts to power up for 2 seconds, then shuts off. After 5 seconds, it attempts to power up again for 2 seconds, the shuts off. It will keep doing this forever and will not power up or boot past this endless cycle. I have been able to get into BIOS, but the system freezes after a minute or two, whereby I must manually restart, and it goes back into its endless power up effort. Four days ago, it would eventually boot up successfully after about 25 tries, whereby I reinstalled Vista. But yesterday it decided it was over it, and now will not boot up. [bleep], it won't stay powered up for longer than 2 seconds now...

So, the computer is very clean internally and not overheating. I tried reseating and cleaning every connection. As stated, I have reinstalled Vista but that didn't help anything. I tried resetting CMOS. I also bought a new hard drive, but nothing changed. My PSU is not overloaded. The mobo shows no signs of having overheated either. I have not changed anything recently to have caused the problem. And when the computer would eventually boot up, there were no other problems, except that asking the computer to restart would cause it to fully power down before powering back up...Any thoughts? Help me, please!

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Hi adriane28 sorry to hear you are having this issue.
You need to provide more information about your computer, this
should include, is it custom build or a brand name such as Dell,
Hp, model name or number, MB, CPU, MEM, any add on card details
and psu make and model, this information will enable others to
help you better.

[phillpower2]

Hi adriane28 sorry to hear you are having this issue.
You need to provide more information about your computer, this
should include, is it custom build or a brand name such as Dell,
Hp, model name or number, MB, CPU, MEM, any add on card details
and psu make and model, this information will enable others to
help you better.

[Digerati]

In addition to the HW information requested, does the CPU fan spin? My "guess" at this point is the PSU has failed.

Also, I am not clear what you mean by "POST/BIOS login screen". The "Windows login screen" is well after the POST. And you don't normally have a BIOS log in screen, unless you set a password for that, and most people don't.

[adriane28]

Hi and thanks for any help... The screen I am referring to comes before the Windows login screen. It displays the maker of my mobo, and simply has the instructions along the bottom, press delete for BIOS, etc. I never figured the name of this screen out...

And yes, the CPU fan spins, lights start to come on, it really looks like, for about one second, that everything is normal, then the whole thing turns off...

[Digerati]

The screen I am referring to comes before the Windows login screen. It displays the maker of my mobo, and simply has the instructions along the bottom, press delete for BIOS, etc. I never figured the name of this screen out...

Okay, I'm with you now. I don't think there is a set name for that screen. It is the BIOS Setup Menu prompt.

Fans run off 12V but the PSU must also provide 5V and 3.3V. Sadly, a bad CPU can give those symptoms, but so can a failed PSU which is where I would start first. Below is my canned text on testing PSUs.

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

Swapping in a known good supply is a tried and trued method of troubleshooting, used for years even by pros. If you have access to a suitably sized, spare power supply, carefully remove the suspect supply and replace it with a known good one and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

Note the required voltage tolerance ranges:

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.

[adriane28]

Thank you for all that information. What are the chances the PSU is fine and it's the motherboard that's fried?

[Digerati]

Yeah, that's possible too. And sadly, in extreme cases, anything plugged into the motherboard could have gone too - such as the CPU and RAM. But in any event, before replacing the engine, you need to make sure you have gas in the tank - so it is best to start the troubleshooting process by making sure you are feeding your electronics good, clean power.

[adriane28]

Okay I have a fresh, new Thermaltake 500w PSU supplying 25w on 12V+ and nothing is has changed. I don't think the PSU, HDD, RAM, Vista, BIOS or CMOS is the problem... Motherboard? What else could cause this mysterious load of crap?

[Digerati]

Sadly, it does look like the motherboard, or CPU. And without trying a spare CPU, there is no way to determine which one. If that was a retail boxed CPU from AMD or Intel, it is warrentied for 3 years. Motherboards are typicall 1 or 3. If this system was factory made (Dell, HP, etc.) you may need to contact them.

[adriane28]

Sadly, it does look like the motherboard, or CPU. And without trying a spare CPU, there is no way to determine which one. If that was a retail boxed CPU from AMD or Intel, it is warrentied for 3 years. Motherboards are typicall 1 or 3. If this system was factory made (Dell, HP, etc.) you may need to contact them.

well, after all this time and anguish, it was the motherboard. slammed a new one in there and she's back to normal, maybe even a little faster! thanks for all the help!!!

[Digerati]

Glad you got it going and thanks for the follow up.