Is this capacitor bad?

Sure looks bad to me, never see one where case was so malformed.

Aldo look for :




Regards, Dana.

Doesn't look bad to me, in the many thousands of faulty capacitors I've never seen a faulty one looking like that.

It looks fairly obviously that it's just the plastic covering on the capacitor that's been subjected to external heat and melted it somewhat.

Easy to check, just cut through the 'bump' with a sharp knife, and see if the can is bulging underneath - it's pretty well 100% that it won't be - but there's always that 0.000....1% chance

Dana's pictures are the classic examples of faulty sub-standard capacitors, although the one on the right may very well be faulty as well. Visual checks are fine, but only indicates a capacitor is faulty (like the first two), not that a capacitor is good.

Out of the thousands of faulty ones I've changed probably around 5% looked visually perfect.

On the other hand, the two on the left may well be perfectly fine as well - but even if they check perfect (on an ESR meter) they MUST be replaced, as they will fail in the VERY near future.

@OP

Looks like electrolyte stain on PCB around that cap ? Eg. leakage out
of cap. Maybe google that condition for more examples to help you
judge.

Or heat distortion of cap plastic, but one would think whole cap would
be involved.....


Regards, Dana.

edd111 said:

Does the below bulging mean the capacitor is bad

Click to expand...

I don't think that I have seen anything like that in many years of abusing electronic stuff!

I suggest that you carefully cut into the bulging plastic with a sharp scalpel or similar.

If it is just heat* distortion of the plastic sleeve, then carry on, it is probably OK.
If it is full of juices and gunk, you need a new capacitor.

* the 39K resistor looks as though it runs quite warm, it could be that which has affected the plastic sleeve on the capacitor.

JimB

danadak said:

@OP

Looks like electrolyte stain on PCB around that cap ? Eg. leakage out
of cap.

Click to expand...

Looks like conformal coating to me, not capacitor leakage - but as I said, just cut the plastic and all will become obvious. But I'd bet money that all that's inside it is abubble of air.

JimB said:

* the 39K resistor looks as though it runs quite warm, it could be that which has affected the plastic sleeve on the capacitor.

Click to expand...

Possibly, but I'm less convinced due to the distance the 'bulge' runs along the capacitor, if the resistor was at the side of the capacitor, then it would be more plausible - but weird things happen

JimB

Odd though, R has no discoloration, and cap with alum foil in it you would think
would distribute its own heat evenly, unless it shorted and took out the supply feeding it.

And then you have array of smd Rs just to its left, coated with something that looks evil.

Whole pic is just odd.....


Regards, Dana.

danadak said:

Whole pic is just odd.....

Click to expand...

We agree on that!

JimB

Nigel Goodwin said:

It looks fairly obviously that it's just the plastic covering on the capacitor that's been subjected to external heat and melted it somewhat.

Click to expand...

Just a dumb question about what you said. How much heat would be needed to reverse a heat shrink wrapper? I think you'll find the plastic on a cap is a heatshrink item. not something glued on.

shortbus= said:

Just a dumb question about what you said. How much heat would be needed to reverse a heat shrink wrapper? I think you'll find the plastic on a cap is a heatshrink item. not something glued on.

Click to expand...

I suspect ageing completely destroys it's heat-shrinking ability - but as I've said all along (as have others), he should simply cut the plastic and look

Seems odd to me – so much discussion yet no one has asked if the top of the cap is bulging.

Personally, I'd replace it since the unit is apart anyway. It looks like it's been distressed and the cost isn't that great.

For The Popcorn said:

Seems odd to me – so much discussion yet no one has asked if the top of the cap is bulging.

Click to expand...

No real need, it's the reservoir capacitor, so only runs at 100/120Hz, and it's VERY rare for those to bulge - they do go faulty very occasionally, but when they do there's normally no physical signs.

For The Popcorn said:

Personally, I'd replace it since the unit is apart anyway. It looks like it's been distressed and the cost isn't that great.

Click to expand...

I wouldn't consider it 'distressed', just purely cosmetic.

But as the board is fully functional, why replace it with a part that might not be as good?.