When your computer suddenly stops booting
 

This HP Pavilion desktop computer has been loyal to me for several years now (and of course, it has Linux on it :)).

Today, as usual, I turned it on (pushed the button).
The leds turned on, and the fans started humming, but there is no output on the screen (nothing). No error messages, no BIOS start screen, nothing.
So, I guess this page does not apply because there are no errors that I can read (no access through ssh either).
So, according to this and this, the best thing to do would be to disconnect and unplug all components that I can, see if it boots and then gradually rule out the parts that may be failing.

So, that is what I intend to do this evening...
Is there anything else you could suggest? Hints? Maybe a list of things to check?
Thanks for reading this.

I presume you are sure there is nothing wrong with the monitor. If the memory is easy to get to I would remove and reinstall it first - interchanging slots. If that does not work then do as you suggested.

I'd take a hard look at the external components first; i.e., does the monitor work (can you plug it into another box and see stuff?), does the keyboard work (plug it into another box...). Second, disconnect the power (for all of the following) and open the box -- do you smell a burnt smell? Then blow all the dust out of everywhere you can get at. Disconnect and reconnect every cable one at a time (they do work loose somehow or other). Disconnect and reconnect every board (ditto).

Reconnect the power, turn it on -- if it works, life is good. Otherwise grab a voltmeter and check the voltages out of your power supply (for example, does the disk drive spin up?). If you're missing any one of the voltages, or if they're low, you just found the problem. When you apply power, are the fans cranking up to full blast (they shouldn't, they should run at a normal, quiet level).

If you're lucky, it's the power supply (new one, oh, $40 or so). If you're not (especially if you smelled a burnt odor), well, it's most likely the motherboard (get a replacement for $30-$60 from E-Bay).

It's unfortunate but the blasted things do fail -- could be a capacitor on the motherboard (and you'd have a heck of time finding out which one or ones). You symptoms sound a lot like power supply (but check the thing completely); if not the power supply, then it'll be the processor or the motherboard gave up the ghost, sorry. You can outboard the disk drive on another box (get a gadget for about $30 to do that) or simply install the drive in another box but a failed drive will not also fail the BIOS coming up at boot.

Hope this helps some.

Been there...
 

tronayne already covered it good, but I'll had my 2 cents.
Believe it or not, 1 week ago I spent 5 hours with a computer that had exactly the same problem you are describing here.
Leds ON, fans working, but no output on the screen, nor BIOS beep errors.
The problem I concluded was the RAM, I changed it and the PC started working 100% again.

In case you don't have extra RAM for trying, you could try something (that I also did) with the damaged RAM still in the PC.
Unplug the PC's power, open it and remove the CMOS battery (usually is a coin shaped one), then wait for some minutes, put the battery back, plug the PC's power and boot it.
If your as lucky as me, the PC will boot (with BIOS default config) and you can see if the BIOS POST indicates a memory test failure, if so the PC will probably shut down if you try to boot from the disk and it will not work again unless you do the battery/wait thing again.

My PC was a little old and I could not boot from a USB PEN (nor had I a CD) to use memtest to test the RAM, but that's another thing you could do.


To sum up, test the RAM first and you could save the hours I wasted testing the other components first. Although the first of the first to be tested should be the monitor...

+1 to tronayne and DarkVenger.

Pulling the CMOS battery is the 'quick and dirty' method. It works, but its better to use the clear CMOS jumper, button or swtich. Clearing the CMOS is always the 1st thing I try when I get a computer that cant boot. Its amazing how often just clearing the CMOS will get you back up and running with any more stuffing around.

The lack of beeps suggests that the CPU is not running. That suggests checking the power supply to the CPU. A possible cause of interrupted current is a bad connector on the route to the CPU. Check the connectors and look for any signs of overheating on the pins.

Another possibility is that the CPU is running too hot and the current is being interrupted to prevent it from being damaged. Look for a wall of dust on the top of the heat sink and beneath the CPU fan. A strategy that sometimes works for that is very gentle cleaning with a shaver brush (the type used for cleaning the blades). This should dislodge the dust barrier and allow the air to flow past the heat sink fins once more.

If the CPU has failed then it is likely that things have been getting too hot anyway. It is wise to check all the fans every few months and look for dust deposits. Keeping things dust free helps reduce temperatures and extend semi-conductor life.

It is not easy to check things like failed CPUs. The usual way is to swap components and check them, thus attempting to isolate the problem to a single component. But to do that you need access to other hardware on systems that are not critical.

You _should_ get a "bad CPU" BIOS beep code in most cases if the CPU is bad. I've had it not work in the past though. I think its most likely the motherboard, but thats just a guess.

BTW, I found this when I was looking for the BIOS beep codes for the board in that system-

http://h10025.www1.hp.com/ewfrf/wc/d...c00757531#N422

If you check "clearing CMOS" it shows you where the clear CMOS jumper is, and gives you directions for how to use it.

Yes, my suggested method is the 'quick and dirty' one :), but in my case the CMOS Reset jumper didn't seem to work so I went for the battery...has my patience shrinks the methods get dirtier ;)
But what you say its true, sometimes a simple CMOS Reset makes authentic miracles :cool:

I thought it was easy to find bad capatitors — if they're bulged, torn, or goo leaked out of them, they're bad and must be replaced.

First thing to try is to remove all RAM sticks but one, then swap them out until it boots. If it doesn't boot, then it's probably not the RAM.

This happened to me a month ago. After testing monitors, power supplies, RAM, and so on, I finally had to replace my motherboard.

Its not that easy, sometimes the capacitor is damaged and the only indication is that it's top and/or bottom is slightly rounded...

Its normally not that hard to tell, but you are right DarkVenger, sometimes its tricky.

BTW, for fun have a look at this-

http://www.discovercircuits.com/dc-m...ants-raves.htm

The 'Fake Chinese Capacitors' at bottom right cracks me up every time I see that pic. Not that its only time I've seen pics of that sort of thing-

http://hobbyaudios.blogspot.com/2011...capacitor.html

Yeah, I've had a motherboard that would sometimes fail with the clear CMOS jumper. Super annoying, as that motherboard would sometimes fail to boot, and when I finally would get teh CMOS cleared it would boot with a "Overclocking fialed, returning to stock speed" message or something like that. I wasnt overclocking though....

That board ended up dead, thankfully in the RMA period. Now the replacement is just sitting around until I can find a CPU for it (I replaced the board while I was waiting for the RMA, and sold/traded the setup to my housemate)

It must be either CPU, MB, PSU or monitor, in case of RAM of videocard failure, the unit beeps.

Reminds me of this:

http://www.cracktwo.com/2011/04/chin...ard-drive.html