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Visual inspection of tantalum caps
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rdagger:
I’m troubleshooting and old PCB from the 70’s and I’ve narrowed the problem down to several tantalum caps. I noticed 1 has a small crater. All the tantalums on the board have small circular depressions, but this one is jagged (see pic). Is this indicative of a failure or is it just a blemish in the casing from the manufacturing process?
GadgetBoy:
I can see it's insides. That's probably not a good thing.
DC1MC:
This one is already dead AND rotten, the problem is that it's like in the zombie movies, you look on it, looks normal, you turn your back on it, it's a zombie now and it bites you with flames >:D >:D >:D.
That another way to say that the tantalums at the end of their working life show no external signs of damage, like the elcos, they are just look and behave normal and then they go full short-circuit :wtf:
Kick them all out,
DC1MC
SeanB:
It's 40 years old, it is a moulded case tantalum, it is suspect anyway. Holes that are like that means it popped a bit from pressure to let out the magic smoke, and replacement is in order. Any more of ther same batch on the board replace as well, they will be close to going bang as well. Looks like it has a 10n ceramic chip capacitor in series, so easy to replace with a regular low ESR electrolytic, probably 22uF 25V, as that will be as low ESR as the 10/15 uF 16v capacitor, and will work well on that 5V rail.
Don't know how many i changed as they were EOL, though i was getting them in in packs of 100, and going through packs a week doing so. Must have thrown around 10kg of tantalum slug away at the end of it.
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