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Old 04-28-2007, 11:25 AM   #1 (permalink)
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Default Intermittent Motherboard -- Bad Capacitor?

I have a laptop which works great sometimes and won't even power on at other times. When it's not working, the laptop DOES respond to the power button, but all that happens is that the loading light flashes on/off for 5 or 6 times and then the laptop powers down. The fan does turn on when this happens.

From what i've seen on this motherboard, there's some sort of sticky residue on all the components, and there's dog fur in just about every place on the board and stuck next to and under every component you could think of. I'm probably going to take a day to tear the laptop completely apart to get to the entire motherboard. When I do that, what am i looking for? What can I use to clean out the sticky stuff/dog fur? Should I be looking for a bad capacitor, and can a bad capacitor work intermitently as described? Finally, I assume that I can test capacitors just by using the different modes on my multimeter and matching the meter's measurements with those written on the capacitor, correct?

Thanks

-Matt
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Old 04-28-2007, 11:48 AM   #2 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

Hello,

What laptop do you have? And how long have you had it for? Does this ever happen when plugged up to a power outlet?
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Old 04-28-2007, 12:29 PM   #3 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

One of the best things to use for cleaning computer parts is diluted rubbing alcohol (1/2 water, 1/2 rubbing alcohol). As for determining if you have a bad capacitor, if there is a slight bulge, then you have a bad capacitor. Even one bulging capacitor can be the reason for instability problems.
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Old 04-28-2007, 03:51 PM   #4 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

It's a Dell Inspiron 4150. I'm gonna pull it apart and clean the motherboard with the diluted rubbing alcohol as you suggested, and i'll look for any bulging capacitors. Thanks!

-Matt
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Old 04-28-2007, 04:34 PM   #5 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

Just make sure that everything is dry before you power up. Also when using the diluted rubbing alcohol and water, make sure you pour a little bit on a rag, then wipe the hardware with it, dont pour it directly on any circuits.
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Old 04-28-2007, 06:48 PM   #6 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

Well cleaning it up didn't change a thing. I've stripped the computer of everything BUT the motherboard, 1 ram stick, and the processor with it's heatsink, and it's still unstable. It is still working sometimes, and turning itself off other times. These capacitors are not what i'm sed to, because i'm use to the stand-up cylinder style capacitors. Is there anything other than a capacitor that may cause instablity like this? How can I check these black box-like capacitors?

I really don't want to buy a new board, because this one works 50% of the time, so that makes me think it's just a small problem somewhere at the component level.

Oh, and the main chip on the board (not the processor) shows a little bit of discoloration on one corner of the center piece of it. Could that be my problem?

Thanks
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Old 04-28-2007, 07:47 PM   #7 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

Hello,

What CPU temperatures are you getting?

Also, when in specific does the laptop power down? At random times when booted into Windows XP, only during POST (power on), or a combination of both?

Also just in case, make sure that you clean the thermal interface material from the CPU heatsink surface and CPU, and add a fresh layer each time you take the heatsink off the processor.
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Old 04-28-2007, 08:44 PM   #8 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

I've found the bad components! They're two little black boxes side by side, and they're blown and have oozed a bit onto the board. How do i Identify them so that i can buy replacement components and solder them in, if i can't read the top of them because they're blown?

also, should I be suspecting that some other component caused them to blow?

Thanks!
-Matt
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Old 04-28-2007, 09:52 PM   #9 (permalink)
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Default Re: Intermittent Motherboard -- Bad Capacitor?

I don't know how you would go about identifying them. But if you didn't void your warranty by opening up the laptop, and you still had one, I would image this would be covered. Nothing would have caused them to go, but age and the possibility that you got one of the bad ones.
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