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Computer won't boot

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#1 canager


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Posted 20 February 2009 - 08:18 AM

this problem finally prevented me to use the PC today.

my problem is a bit similar to this:

"...my CPU will not boot up. What happened was that whenever I powerup, the power will come on, everything will start whirring (CPU fan, video card fan, casing fan and everything else that should whir..."

to add to that, here were my observations:
-whenever i turn the power on, i now don't hear the usual "one beep" that comes with the boot up
-the keyboard doesn't seem to light up during boot up (this is not confirmed; i'll check on this later)
-black screen, nothing shows on my monitor. monitor's power button light blinks.
-early today or the other day, monitor turned completely orange w/ vertical blue lines(w/ other colors w/c i forgot). NOTE: last year, i had an LCD moonitor problem w/c already got resolved.
-this happened twice: as i was using the PC, it suddenly restart on its own (re-booted on its own)
-early today or the other day: due to frustration on my internet connection, when i stomped my hand on the table, my PC just restarted. (the PC is on the table)
-***** just the other day, 1 long "beep, beep, beep, beep, ...." when i turned the PC on. worried & alerted , i immediately pressed the power button off. this just happened once.

what i've tried:
-remove the vid. card, 2 sticks of RAM, clean their "contacts", & re-install them.
-remove & re-install all the plugs/cords. (this particular one "seem to have worked" just the other day --see ***** above-- when this "no boot-up" incident happened)

my thought-of possible causes for this problem:
-dead power supply
-dead mobo
-poor ventilation/overheating (no dedicated electric fan for my PC; no aircon in my room)
-minor issue of dirt?? (i will address this tomorrow morning)

i'm sorry i don't memorize the PC specs. all i can remember is i've got dedicated video card (128MB if i remember right) ; 2 sticks of RAM, 512MB each ( 2nd RAM i just bought just 4-8months back), AMD Sempron processor, 300W Power supply; Samsung LCD monitor. my PC is 4-4.5yrs old.

i'm in an internet cafe, so im not sure if i'll be able to get back & answer some questions. but thanks to all who will reply!!

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#2 hamluis



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Posted 20 February 2009 - 11:26 AM

Hi :thumbsup:.

In such instances, my first step is to check all connections.

Second step: Temporarily try a different power supply (I always have a spare on on hand from prior systems).

Doesn't take long and it allows confirmation/refutation of the PSU as a prime suspect.


#3 dc3


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Posted 20 February 2009 - 12:09 PM

If you don't just happen to have an extra PSU sitting around you can use the technique outlined below to test the PSU.

The purpose of this procedure is to bypass the motherboard to test the PSU.

This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle. To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard. Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed. This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.

Posted Image

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.

Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14. If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner. This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom. The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper. For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation. It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing. You are at risk of electrical shock if you are holding the jumper when you power up the PSU. Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.

Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

At this point you can use a DC Voltage meter to read the different rail Voltages. You will want to insert the black probe into any of the Black (-) sockets, and insert the Red (+) probe in the five different colored sockets, one at a time. Below are the five different colors and their corresponding rail voltages. The Voltages should be within about ten percent plus or minus of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC

To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.

Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.





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