Fairly simple question. Other than physical damage from any small explosions, when an old cap blows, what else happens? I've always assumed it just breaks the flow of electricity and nothing else is affected, meaning a cap could be replaced and functionality restored. Is it common for it to take other components down when it dies, in a more complex way like a CPU and motherboard that can kill each other?
Most of what's out on the web really covers spotting or replacing bad caps, not whether it affects components up/downstream.
Other than rather violent blown caps embedding themselves into other tech and or walls, etc, blown caps usually are fixable... But it depends on a variety of things like if the system shuts down after the cap went, or didn't, or if it was a cap that was particurlarly important and without it other things die... So it just depends really.
It really depends on what that cap was responsible for. but for the most part it is as simple as replacing them with new ones. unless the system kept running with the blown cap and for an instance the decoupled VRM has started to heat up and draw more current due to unstable and insufficient power delivery and as a consequence damaged itself. Even this scenario is unlikely to happen unless the system has been running some kind of an overclock and running a certain load for some time.
I'm not sure, do old capacitors actually blow up? They just pop and leak, afaik. If capacitor explodes, it's probably overvoltaged, which means that you have bigger problems elsewhere on the board.
An ideal capacitor doesn't pass any current, unlike a resistor (or a wire which is a very low-value resistor) which passes current. You can think of a capacitor as "absorbing" the current and "dissipating" the current, but never actually passes current through.
A capacitor is constructed of two conductive plates with a VERY non-conductive material separating them. As a capacitor ages, that dielectric in the middle can begin to let current through. As more and more current leaks through the capacitor, it becomes a resistor and the power going through it heats it up like a wire heating element.
In some cases, the heating action of the dielectric separating the plates will actually accelerate the dielectric disintegration. A chain reaction occurs and the plates basically touch each other. If there's enough potential energy across the plates (either in the caps already or in the rest of the circuit) the plates can get so hot when they contact that they create a tiny explosion from the super heated material.
Once caps have reached this catastrophic failure, often they are now "shorted" and YES, creating a short in a circuit where there previously was no current being conducted can absolutely (and very likely) cause many other components to fail. If you're lucky, the explosion forced the plates back apart and the capacitor is now a "break" or open circuit. This is obviously the preferred outcome of a blown cap.
A few years back I dug up an old Socket A board to test out, and as it was running it started popping caps. All of the other hardware worked when I switched it to another board, so it was just the old off-brand motherboard that failed. The amazing part was that a few of them popped and the computer never hung up. I just shut it down in case of any fire hazard.
My understanding is that it is mostly a problem of electrolytic capacitors (they have an electrolyte) vs the solid state capacitors used on boards for a number of years now. If you are trying to fix an older board then it might be better to move the hardware to a different board for testing, but then again that may not be an option.
Electrolytic capacitors last a lot longer if kept cool, heat exponentially shortens their life, this is why power bricks are a bad idea, no internal air flow.
Depending on the circuit and nature of the failure, it can affect other components, yes. But they don't even have to blow up, bulge or start leaking for this to happen.
In this case, the cap behaves like a fuse, and yes, it is the preferred scenario for a failure.
We had an old Philips TV that gradually started behaving odd whenever we'd turn it on. The picture signal took more and more time to "stabilize" upon switching it on, as weeks went by. The first thing that I thought was "capacitor". It had checked all the boxes. 10+ years old TV set, heavily used, failure-over-time instead of just outright dying, strange behavior only initially upon powering up, until it "stabilizes"... So I told my dad and got the usual "no" when I suggested to open it up and take a look at it.
Fast forward a couple of months. It finally dies. We take it to the repair man and describe the behavior of the past few months.
"It should be fixable, come back tomorrow"
The next day we go to pick it up. I ask what was wrong, and basically "several components died, but nothing serious".
Me: So, was one of those components a capacitor?" Him: Yep. If you'd come earlier, the repair would have probably been half the price. That cap took down 3 components with it when it died"
He then explained to me that capacitors can also just lose capacitance over time. They apparently don't even have to bulge to malfunction. They just get old.
tv repair men are becoming completely extinct now....
crazy how (at least in america) our culture is that it's more efficient to just throw something away and get a new one rather than repair it. (speaking of electronics industry mostly)
My point wasn't to go over the merits of which is better, but rather what is being used. There aren't a lot of electrolytic capacitors on modern motherboards in comparison to ones from 10+ years ago, so the chances of finding a blown capacitor today is less likely.
Someone without any electronics experience looking at a modern motherboard would be less likely to find an electrolytic capacitor gone bad simply by looking for ones bulging or blown because there are less of them to see. Someone with great electronics experience probably has methods for testing any type of capacitor and experience in dealing with them that goes well beyond the scope of what a novice would know.