Real talk though, can anyone identify this cap for me and what I need to replace it with?
the board seems to work fine, but i'm sure it affects something so i would like to replace.
I believe those caps are for the ISA slots, which would explain why the rest of the board is still working. If I had to guess, the one that failed there is probably for one of the 12v rails, so any ISA cards that utilize that rail would of course not work.
Does the motherboard have a manfacturer and/or model number on it anywhere?
Yes those tantalum caps can litteraly explode when they are shorted out, it happend to me recently.
Chances are the ISA slots and everything else still work because caps are only for regulation, but the computer might be instable.
Better change the others before they blow out too. That is probably a mobo not used for a very long time.
That's a tantalum cap. Most likely 10µF, 16V. It is used for smoothing the +12V or the -12V line. It's normal for old 16V tantalums to blow up on 12V rails, especially if they were unpowered for a long time. After the cap blew up, it doesn't disturb the circuit any more (but it also doesn't smooth the voltage). During the blow-up it was a short circuit momentarily, but then it burnt up and interrupted the short circuit like a fuse.
Regarding exploding tantalums, some YouTuber (maybe on Adrian's Digital Basement, maybe RetroSpector78) shouted at a tantalum capacitor: "Hey! This is a non-smoker's area!". Tantalums only disturb operation if they are shorted, but not (yet) burnt. If a IBM PC or XT (the original 5150 and 5160) don't power up, one ore multiple shorted tantalum caps are the most likely cause today.
mscdex wrote on 2023-01-22, 20:20:I believe those caps are for the ISA slots, which would explain why the rest of the board is still working. If I had to guess, the one that failed there is probably for one of the 12v rails, so any ISA cards that utilize that rail would of course not work.
Does the motherboard have a manfacturer and/or model number on it anywhere?
I couldn't find a likeness to it on the retro web. here are some pics. I think it's an AOpen of some sort based off the logo in the corner.
I think this is your board?
https://theretroweb.com/motherboards/s/acer-i … gxi-model-i433a
pico1180 wrote on 2023-01-22, 18:36:Real talk though, can anyone identify this cap for me and what I need to replace it with?
the board seems to work fine, but i'm sure it affects something so i would like to replace.
Tantalum capacitors, they can crack for various reasons (including manufacturing defects) and will invite oxygen and moisture, which will cause local shorts. Blows up when powered, can keep glowing and smoking while power is still applied so a bit of a fire hazard.
Replace with modern tantalum of 25V rating, capacity between 22uF and 100uF (47uF is a good choice if you can't see the markings on the nearby caps, it's not really critical). There is no need for alarm if one cap on old mobo blows up, but two (or more) would suggest that all of them should be replaced. Frankly these days you can get low-ESR electrolytic caps that will outlive you and not blow up (unless polarity is not observed) so you can go this way if you can't have any more such surprises in the future.
Deunan wrote on 2023-01-23, 12:35:pico1180 wrote on 2023-01-22, 18:36:Real talk though, can anyone identify this cap for me and what I need to replace it with?
the board seems to work fine, but i'm sure it affects something so i would like to replace.
Tantalum capacitors, they can crack for various reasons (including manufacturing defects) and will invite oxygen and moisture, which will cause local shorts. Blows up when powered, can keep glowing and smoking while power is still applied so a bit of a fire hazard.
Replace with modern tantalum of 25V rating, capacity between 22uF and 100uF (47uF is a good choice if you can't see the markings on the nearby caps, it's not really critical). There is no need for alarm if one cap on old mobo blows up, but two (or more) would suggest that all of them should be replaced. Frankly these days you can get low-ESR electrolytic caps that will outlive you and not blow up (unless polarity is not observed) so you can go this way if you can't have any more such surprises in the future.
I replaced with an 10µF, 16V. It seems to be functioning fine.
pico1180 wrote on 2023-01-23, 20:42:[...]
I replaced with an 10µF, 16V. It seems to be functioning fine.
Out of interest:
Tantalum or electrolytic?
These tantalum caps are about the only reason I'm relieved to have to wear glasses these days - less chance of the debris of an exploding beastie blinding me. Had a bit of a close shave once, a fragment hit my eyebrow. Then again, I also almost got a fountain coming out of a cap plague era electrolytic in my eye once too...
dionb wrote on 2023-01-24, 01:10:Out of interest: Tantalum or electrolytic? […]
pico1180 wrote on 2023-01-23, 20:42:[...]
I replaced with an 10µF, 16V. It seems to be functioning fine.
Out of interest:
Tantalum or electrolytic?These tantalum caps are about the only reason I'm relieved to have to wear glasses these days - less chance of the debris of an exploding beastie blinding me. Had a bit of a close shave once, a fragment hit my eyebrow. Then again, I also almost got a fountain coming out of a cap plague era electrolytic in my eye once too...
Electrolytic
I know this is not really recommended by most people but when filtering tantalum caps explode on me (that most usually happens to the ones near the AT power connector in my experience) I replace all of them with electrolytics. If one exploded, the rest are ticking bombs anyway and I can't be assed with replacing them with time bombs with longer fuses..
I think in the case of exploding tantalum caps, especially if it happened more than once and/or you are really worried about starting a fire or causing damage to some expensive cards, a total recap is not a bad idea. I'm against shotgun recapping because most people do it just because they can, not due to actual need for such extensive repair. But the "teardrop" caps on old mobos are one of the few exceptions where such preventive measures make some sense and it doesn't bother me, even if it's not something I would do myself.
BTW modern teardrop tantalum caps, of good brand anyway, are tested in production for high dV/dt charging spikes (this is what also causes stress and cracking). So should be much more reliable. And then there are wet tantalum caps, same extremly active metal but completly different construction - I'v yet to see one of those fail. Still manufactured in pretty much same way as in the '70 and used in aerospace and military applications - if it aint broke, don't fix it.
I don't think tantalum caps could start a fire when exploding but it sure can damage nearby boards.
Ha! I thought so too until one of these capacitors turned into a pretty bright glow plug right in front of me - and this didn't trip the PSU. So with right circumstances there might be something flammable like wire insulation or piece of plastic close to such capacitor, and it might catch fire. Yes I realize this is a remote possibility but now I'm aware of it and I always makes sure any of my builds - be it in a case or open-air, are done in a such way as to avoid any possible flame spread. That's in case I need to leave a powered old mobo unattended for some time - better safe then sorry.
it may not have damaged my board, thankfully, but this happened on my test bench with my face about 12 inches away from the board. the only thing damaged besides the board were my shorts.
