Hardware question: PC auto shuts down....

Greetings!

i have another PC.
i bought a 22-inch Chimei LCD, for that PC, back in February. i have seldom used that PC since then.
i have encountered a problem with it, which has never happened before ---- the PC automatically shuts down. it happened again today (it's the 2nd or 3rd time it happened).
pressing the power button does not/cannot turn the PC on (PC does not boot). but i noticed the keyboard & mouse are still lit on (remember the PC is off). i can turn the monitor on too, but of course, there is no image/monitor is black.

the last time it happened... what i did was let the PC rest for a few minutes, reconnect the power cords to the AVR (auto. voltage regulator), then it turns on & works ok, like nothing happened.

if it helps, that PC has been having a ringing sound during boot time, since mid2009-Jan2010.

i do not have an idea what the cause is.
but my guess is that the problem has something to do with the new monitor.
the old monitor was a 15" samsung LCD.
..another guess is the power supply. since i upgraded to a bigger monitor, this may be related to it. (a few minutes ago, right after the PC auto shut down, i touched the Power supply casing it was relatively hot)
my power supply is 300W, it came with the PC when i bought/assembled it around 6yrs ago..


Hopefully someone can help
Thanks all!

300W? What are the specs?

Also, what sort of ringing sound? Something coming from the internal PC speakers? Or something else?

Sounds like you think it's the power supply. Why not just upgrade it?

Ronald Raygun,
it's an old PC. bought it around 2004.
i do not remember all the specs. (got amnesia too, lol)
AMD Sempron
1.5GB RAM
NVidia FX5500 256MB video card

from what i've observed, the ringing sound seem to come from the power supply. but i may be wrong.
how do i describe the sound? it sounds as if "it's hanging on for dear life"*.

the ringing sound from boot time:
wrrrrrrrrrrrrrrrrrrrrrrrrr........................ {this happen for about 5-10seconds}
*wrrrr... ( </= 1second pause)... wrrr... ( </= 1second pause) {this part repeats about 5 - 10 times}
wrrrrrrrrrrrrrrrrrrrrrrrrrrrrr..... (the ringing sound slowly dies down).
the total sound duration is about +/-15 - 20 seconds from start of boot up.

are there other possibilities aside from the PS?
Thank you!



Rabid,
heheh
i do not have too much money. & i live below my means.
i only buy stuff when it's inevitable &/or necessary.
& i'm Asian
Thank you!

i had the same problem on an old machine i had it was the video in my case i dont know what it was but it would work for say 10 15 minutes i would walk away to do something come back and the computer was off but keyboard was on like you say. i just changed that out and it was fine. the only other thing i can think of is power supply like you have already said.

regards damien

I have no idea what your hearing range is like, but generally speaking, a high pitched noise from a computer usually means a capacitor is busted or about to break somewhere.

Capacitors are found almost everywhere on a computer--especially the power supply. Perhaps you have another computer to swap power supplies with?

Another possibility is overheating. Is it possible the computer is going into a protective shutdown because it thinks it's overheating?

Diagnosing hardware problems is easy. It's done by bisecting the problem into smaller increments.

Start by unplugging all of the drives, hard drive, floppy, CD-rom, etc. Also, disconnect all of the
non-cruicial expansion cards (aka everything but the video card).

Boot computer...

Does it continue? If not, then you know it's one of the devices you took out. if so, then you know it's
one of the devices you left in.

If it continues, then it's either the video card, the motherboard, a fan, the processor, or the power
supply. You can repeat this process with whatever components you have till you have the problem
isolated.

If the sound is coming from the PSU, it's probably the fan on the PSU. A power supply is nothing but
a set of capacitors and chips, cooled by a fan. If the PSU fan is clogged, or dying, then it will overheat
and make a whiney noise. If it overheats, it might shut down (and could damage other components).
You can get a temperature program and see if it's a temperature issue. That's easy to determine.

You can get software to read the voltages if you want, that might help provide a clue. But if you do
the disconnection process and the problem persists, it's prolly the PSU. Atleast that's a good first step.

will check the capacitors...
yes, i'll try this PC's PSU.
overheating seems possible too. i hope it created no peripheral damage.



****************
ok, based on all your posts,
it really is possible that there are other culprits aside from the power supply.

i have been reading up on online related articles as i wait for replies here.
what's been mentioned here are echoed in the articles.
i'll try to isolate the issue by checking each component.
Hopefully i'll get to fix it soon.

Thank you very much Ronald Raygun, Rabid, & damosdmf

Quick and dirty method to test the PS:

Thanks Slack!
almost forgot about watching those free videos.
just watched a few videos..


free Power supply wattage calculator
http://extreme.outervision.com/PSUEngine
or
http://www.thermaltake.outervision.com/

based on an elimination process, i've singled out the power supply unit.
so my initial hunch was correct.

i bought a new one a few hours earlier.
i just tried it.
during the first attempt i still heard a ringing sound, but it was considerably shorter in duration & quieter in volume. (video card may be another culprit)
during the second attempt, it went smoothly.
Thank God.
will monitor it for about a week.

Thanks to all who replied!
God bless

supreme,
Sounds like you fixed it? , given that you still had lights on sounds to me like she's going to sleep. by replacing the monitor check that it has not altered the sleep settings of the pc (control panel/ systems and maintenance/ power options) and if it's anything like my pc when its gone to sleep, its like trying to play the Blackpool tower ball room wurlitzer to find out which key gets her going again!!!!!



regards

doc