I don't usually take capacitors apart...
so here is a little Teapo/Yageo autospy. The SC series tends to develop various failures. One is a dried 1000/16 Teapo from psu's 5vsb. Bulging and dry.
Second is a 2700/6.3 Yageo from a socket A motherboard's vrm; Not bulging, but the capacitance is way up and has some sort of corrosion inside.
Second is a 2700/6.3 Yageo from a socket A motherboard's vrm; Not bulging, but the capacitance is way up and has some sort of corrosion inside.
I'm glad you measured the capacitance and posted a screenshot. Virtually all my bad caps measure much lower in capacitance with a multimeter.
Tom66 was the first person that I know who said some of his failed caps showed higher capacitance. Now we have more evidence.
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I think the elevated capacitance indicates a 'lytic whose water-based electrolyte lacks the necessary inhibitor and is attacking the aluminum oxide dielectric layer. Thinning that will raise the capacitance while lowering the maximum volltage. That process would end when the maximum voltage fell below the circuit voltage, and the cap either vented or launched.
PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
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To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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Failing 'lytics can get reeeeally hot if they don't vent quickly. OTOH, watching a 'lytic vent can be very entertaining.
PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
****************************
To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
****************************
OTOH, watching a 'lytic vent can be very entertaining.
Too bad they smell so nasty. Lytics with no vents are even more fun.
Originally posted by PeteS in CA
Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
It's not roll of aluminium if I remember correctly. It's roll of a dielectric (paper, film, other materials) and between layers of the roll there's electrolytic substance.
They explode when the electrolytic turns to gas and increases the pressure inside, causing the aluminum can to burst out of the bottom plastic or simply crack where the aluminium can has some flaw and the plastic bottom is too well locked in place..
They burn when they're shorted and the electrolytic leaked already through the vent or porous plastic bottom.
The electrolyte is part of the current path in an electrolytic capacitor; the paper helps hold it in suspension between the aluminum foils. Neither the electrolyte nor the paper is the dielectric. The dielectric is a thin layer of aluminum oxide formed on the aluminum anode foil. If the electrolyte dries out (I^2 * R self-heating and/or a nearby external heat source) or leaks out, there is no current, and no heat. Internal heat happens when there is too much current or unwanted chemical reactions happen (e.g. the applied voltage is too high, the electrolyte has thinned the aluminum oxide dielectric layer (lowering the maximum voltage) or is reverse polarity). Internal gas pressure can build, due to the heat and/or due to rapid forming of the oxide layer (over-voltage or reverse voltage). If the pressure gets too high, something gives. It might be the vent scored into the top of the can; lacking that, the can might pop its bottom, by lifting just enough to release the pressure or by launching (which does relieve the pressure).
PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
****************************
To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
****************************
I would have really struggled removing the heat sink mount if I hadn't found this forum, I would probably be looking for small bolts to replace the chewed up plastic pins about now instead of installing windows updates.
Hey so I really don't know if these are bad, it's just that all of the brown coloured one on this motherboard which is from 2008 are bulged out except for 1 which is visible in the second photo. What happened was a couple weeks ago there was this jack*ss electrician who shorted the whole circuit to the office and blew 2 PCs, this one still worked but now it turns on and hangs in windows. Booting with a CD that tests RAM hangs and so does the CPU test (UBCD 2011). Sometimes the PC won't turn on (black screen), I have to turn it off and try a few times. I would be real keen to try replacing the caps if someone else can tell me if these are really bad or they are supposed to look this way, there is no leakage or anything else but a faint smell comes from the board but it could just be my imagination.. It's a HP Compaq dx7400... What ya reckon? I guess my real question is, are there any 'Good' caps that have slight bulges, it just seems odd that it happened to almost all of the brown ones but not the other (guess the others are better quality)..
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Last edited by timb0; 05-16-2012, 07:09 AM.
Reason: tidy up..
The swollen ones have to be replaced. They're going bad, maybe already outside their specs.
The ones near them should also be replaced. They don't show signs of going bad, but maybe they simply were better built or they just had less electrolytic than the others and didn't generate enough gas to cause pressure on the top.
Either way, you should replace all, they're certainly a cause for your problems..
Start a separate thread in the proper section (motherboards) with the writing on the capacitors and we'll suggest replacements.
Those are Tk caps, known crap brand. Definitely replace all in the CPU VRM area, and around the chipset as well.
Originally posted by PeteS in CA
Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
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