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Last summer I left for extended holidays and left my laptop in my desk for about 3 months. It wasn't plugged in but I didn't remove the battery and I might even have left it sleeping. When I got back, I started it, plugged it in, and started using it as normal. After about 25 minutes, it abruptly reset. Subsequent attempts to start it resulted in the same behaviour with increasingly short times between boot and reset.

I didn't have time to look at it just then so I left it alone, with the battery out, for about a week or two. When I came back to it, it had the same behaviour, although the time between boot and reset was longer again and then gradually getting shorter (from ~10-15 minutes down to about 500ms in just a few iterations).

The processor doesn't seem to get hot, and the RAM isn't faulty (I checked it in another machine). It runs Ubuntu, although I don't think the OS has anything to do with this. It's an HP Pavillion dv6 with a 64-bit AMD Athlon X2 and an ATI Radeon (mobile, I think) graphics card. It was working fine and I hadn't done any overclocking.

How would I go about finding more about this failure, and eventually resolve it?

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Have you checked for dust buildup? –  user3463 Jun 10 '12 at 5:33
    
Will do when I open up everything again. Doesn't look dusty from just the RAM+HDD+PCI panels, though. –  Félix Saparelli Jun 10 '12 at 5:37
    
There's a bit of dust near the fan, nothing major though, airflow seems normal(ish). –  Félix Saparelli Jun 10 '12 at 7:19
    
Does it do the same thing with the battery removed running on external power only? –  Tyler Faile Jun 11 '12 at 17:44
    
Yes. But I think I have found the problem after completely disassembling the laptop: the CPU thermal grease has dried off. I have ordered a new tube and will post again when I get it :) –  Félix Saparelli Jun 18 '12 at 5:10

2 Answers 2

I have seen this sort of issue on computers that have leaky or bulging capacitors.

Computer symptoms

Some common behavioural symptoms of "bad caps" seen in computer systems are:

  • Intermittent failure to turn on, requiring user to press reset or try turning the computer on repeatedly
  • Instabilities (hangs, occurrences of the "Blue Screen of Death", kernel panics, etc.), especially when symptoms get progressively more frequent over time
  • Memory errors, especially ones that get more frequent with time
  • Spontaneous restarts or resets
  • In on-board or add-on video cards, unstable image in some video modes
  • Failure to complete the Power-On Self Test ("POST"), or spontaneous rebooting before it is completed
  • Failure to even start the POST; fans spin but the system appears dead

(Source: http://en.wikipedia.org/wiki/Capacitor_plague)

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I don't think this is the problem. The symptoms I observe are very deterministic, they happen the same every time I try (every few days/weeks when I get motivated enough), it doesn't seem to get worse over time. Moreover, I have now the entire MB exposed, and there are no leaky or bulging capacitors afaics. –  Félix Saparelli Jun 10 '12 at 7:19

May be your battery level is damn down that you cant boot it up, whatever you are plugged, but may be consumption rate is higher than charging rate.

Plug it, and leave it for few hours.. and then try to start it as usual...

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