   find and fix bad capacitors
  Is there a way to see or detect if capacitors on a motherboard are bad?Is it possible for them to be bad, but where you can't see it on the outside?Is it possible to replace bad capacitors from a motherboard and use it again afterwards?   
  First of all, I'd have to ask - why are you thinking you might have a bad capacitor or two? Is your motherboard having any specific problems, or, is it a more general question..Now, onto your actual question... the easiest way to see if a capacitor (specifically an electrolytic capacitor - as there's been a lot of talk in the past about "bad batches") is bad is to look at it and see if either (a) it is bulging on top, or (b) it is actually leaking electrolytic fluid (nasty stuff)... Most newer motherboards have been switching to more to solid capacitors (without fluid inside) so they've been much more stable...For testing them, it is possible to test with a multimeter (see: http://www.repairfaq.org/sam/captest.htm#cttcm for a reference), but they also make specific tools to test.You can replace them, if you have a really good soldering iron and steady hands (and know a bit about electronics!), but if you're a novice, it's best left to professionals...Also, here's some decent links:http://www.pcstats.com/articleview.cfm?articleID=195http://en.wikipedia.org/wiki/Capacitor_plague;Quote:Original post by DJHoyFirst of all, I'd have to ask - why are you thinking you might have a bad capacitor or two? Is your motherboard having any specific problems, or, is it a more general question..This is about the computer I've been having for 5 years now. Recently I've built a new computer, but I still need this old one.This old one has been showing problems already since it was a year old. Very sometimes there was a sudden random crash for no reason. There have been times when it was about once a day, and then there were periods when it hasn't shown any problems at all for many months, and then later randomly it did it again. It was OS-independant, so certainly not driver dependant. I did a memtest, and made the memtest run for a whole night, and there were 0 errors. I then always suspected the videocard, because the errors were usually video card related (video card drivers mentioned in the crashlogs).Then about a year ago, it had a different kind of symptom: sometimes when booting up, the motherboard started making a sequence of low/high/low/high/... pitched beeps. Pressing the reset button made it boot up fine then. Since there was that easy solution of just resetting, I never really did anything about it. After about a month, that beeping problem disappeared again mysteriously.But now the computer is again in a bad period. Now, when booting up, I can go to KDE in Linux, and after a minute it'll freeze. Then I reboot again, to KDE again, after two minutes, it freezes again. I also tried it with booting to MS Windows, and same thing: it freezes after a while. Sometimes it also reboots after being frozen for a few seconds.Then I was like, let's look in the BIOS at the temperatures. So I boot to the BIOS and all voltages and temperatures look normal. But then, it freezes again. My computer actually managed to freeze while in the BIOS menu :)I've mentioned all these freezing problems, but after rebooting enough times it'll stay on without freezing for more than 5 minutes, and then it remains on and is rock-stable.That made me think that it's not really a faulty RAM, not a faulty video card, or bad CPU, but some electronic component that appearantly is sometimes unstable and after a while settles in and works longer, or maybe isn't needed anymore once a certain temperature is reached or so. And so couldn't that be a bad capacitor on the motherboard?BTW if it is a bad capacitor, is there any danger that other components may get damaged if I keep using it?   ;  It could be a lifted trace, as well, or a dirty socket of some kind. I've had a few little glitches that turned out to be a dust bunny partially blocking one of the RAM pins.There's a whole host of electronics problems that could exist.Outside of the obviously damaged capacitors (i.e. leaking) I can't think of any obvious way to discern defective caps. If you figured out which ones were damaged and were really, really good with a soldering iron, you could replace them with ones that take the same load. But that's an extremely difficult task.Might just be best to toss this one in the skip and buy a new machine to hold the old box's data.   ;  Just an idea, but have you checked the power supply ?   ;  It sounds like the power supply could be an issue... especially if it's overheating due to dirt... definitely take a can of air and clean out all the dust from inside and on the motherboard - (I've seen too many systems burn out due to dust buildup overheating the internals...)also - in your BIOS settings, have you overclocked anything? It could be something is overclocked, getting too hot and causing havoc there... You may also want to remove and re-seat the RAM, and possibly (if it is still not working), remove the CPU, clean off any and ALL existing thermal grease, reapply new thermal grease and re-seat it...From this:Quote:I've mentioned all these freezing problems, but after rebooting enough times it'll stay on without freezing for more than 5 minutes, and then it remains on and is rock-stable. If it was a capacitor problem, you would probably not get a rock-stable system at all...Other than that, I'd have to agree with Ravuya - it can be a whole host of other problems, and it just very well may be time to upgrade...   ;  I haven't found any leaking or imploded capacitors, so maybe they're not the problem after all, luckily (or not because no obvious cause is found).I've given the computer a very thorough vacuum cleaning job. There was a lot of dust indeed but nothing that seemed to cause short circuits. It hasn't crashed yet today, but that doesn't mean anything with this really unpredictable computer, it could as well crash just after I made this post :)EDIT: yup crashed again now, same symptoms. Stupid machine.[Edited by - Lode on September 8, 2007 3:24:22 AM];  I had a similar problem with a PC.  Turned out it was a crappy power supply.   ;  This thing is making me crazy.The power supply isn't really the best one indeed: 300W, made in China, brandless.However if I look in the BIOS hardware monitor, the voltages are all normal. If the voltages are normal, it's ok, right?If I look in the BIOS at the voltages sometimes it freezes too. But the frozen voltages on screen are still all within the range. So either it's not the power supply, or it's the power supply but something else than the voltages (is that possible?), or the voltage really becomes out of range but the BIOS doesn't react fast enough to show this on screen before it's frozen.Here's some of the things that happened yesterday and today:I boot up, work in KDE for 20 minutes, then suddenly it freezes and my music is stuck in a loop. It auto reboots then after a few seconds.I go to the BIOS menu to look at the hardware monitor to see the voltages. The BIOS shows voltages that are all in range. I press a key on my keyboard and notice that the BIOS doesn't respond to my keyboard! It's still updating the values on screen, but yet there's no response at all to the keyboard anymore!I press the reset button, and the screen remains black with its power light indicating standby. I turn off the power a few times, and after a few retries, the computer boots up again, in KDE again.10 minutes later, while I'm compiling some code, it freezes again! I press reset again and the screen remains black again. I press reset many more times and after a while it boots up again and I'm now able to type this text on it.The weirdest, new, thing, now is that the keyboard wasn't working while the screen was still updating with new values in the BIOS. What can that indicate?Another new thing is the black screen when rebooting :(I really hate this kind of unpredictable computer problem, WHAT IS THIS?Luckily, I use this dreaded machine only in the weekends when I'm at my parents place, but still...I will try a new power supply if I have one available.   