Can you tell if a capacitor leaked by dissecting, and looking at the brown paper?

[bryanska]

Originally posted in Sci.Electronics.Repair, but everyone wants to
dance around my question. Does anyone here have the answer?

Can you tell if a capacitor has leaked by dissecting it?

My JVC stereo is humming loudly. There are signs of an obvious
capacitor leak around three large capacitors on the board. Brown crust.



I replaced two large 6800uf 40v caps, but the humming remains. So I
pulled the third cap, a smaller 3300uf 35v unit.


For fun, I dissected all three.


Each large 6800uf cap had dark brown paper all the way through. Viewed
from the top, the spiral of paper was consistent in color.


But the smaller 3300uf unit, when the paper spiral was viewed from
above, the center of the spiral was a lighter color than the rest of
the paper.


Does this mean I have found the leaky unit?


I have no way to test them.


PS

1) I am QUITE sure it wasn't glue used to hold down the capacitors.

2) I know the electrolyte is acidic, okay?

3) I know all about Usenet, and that I can't control responses of
others. But please, please try and answer my question?

 

[bryanska]

Added some pics on Flicker.

Doesn't it seem odd, that the cap's fluid is so poorly distributed?

http://www.flickr.com/photos/67108618@N00/

 

[Eeyore]

Originally posted in Sci.Electronics.Repair, but everyone wants to
dance around my question. Does anyone here have the answer?

Can you tell if a capacitor has leaked by dissecting it?

No. You can tell by the leak though !

Graham

 

[Al]

Originally posted in Sci.Electronics.Repair, but everyone wants to
dance around my question. Does anyone here have the answer?

Can you tell if a capacitor has leaked by dissecting it?

My JVC stereo is humming loudly. There are signs of an obvious
capacitor leak around three large capacitors on the board. Brown crust.



I replaced two large 6800uf 40v caps, but the humming remains. So I
pulled the third cap, a smaller 3300uf 35v unit.


For fun, I dissected all three.


Each large 6800uf cap had dark brown paper all the way through. Viewed
from the top, the spiral of paper was consistent in color.


But the smaller 3300uf unit, when the paper spiral was viewed from
above, the center of the spiral was a lighter color than the rest of
the paper.


Does this mean I have found the leaky unit?


I have no way to test them.


PS

1) I am QUITE sure it wasn't glue used to hold down the capacitors.

2) I know the electrolyte is acidic, okay?

3) I know all about Usenet, and that I can't control responses of
others. But please, please try and answer my question?

The paper should be light in color and damp. It should have an
ammonia-like odor to it. If it feels dry, yes the electrolyte leaked
out. Most electrolytics have a vent in the seal at the terminal end.
Over time they tend to dry out. As ambient temperature and atmospheric
pressure change, the liquid is "pumped out" as vapor. They dry out even
faster if they are passing too much AC current.

Al

 

[legg]

Originally posted in Sci.Electronics.Repair, but everyone wants to
dance around my question. Does anyone here have the answer?

Can you tell if a capacitor has leaked by dissecting it?

My JVC stereo is humming loudly. There are signs of an obvious
capacitor leak around three large capacitors on the board. Brown crust.



I replaced two large 6800uf 40v caps, but the humming remains. So I
pulled the third cap, a smaller 3300uf 35v unit.


For fun, I dissected all three.


Each large 6800uf cap had dark brown paper all the way through. Viewed
from the top, the spiral of paper was consistent in color.


But the smaller 3300uf unit, when the paper spiral was viewed from
above, the center of the spiral was a lighter color than the rest of
the paper.


Does this mean I have found the leaky unit?


I have no way to test them.


PS

1) I am QUITE sure it wasn't glue used to hold down the capacitors.

2) I know the electrolyte is acidic, okay?

3) I know all about Usenet, and that I can't control responses of
others. But please, please try and answer my question?

If you dissect it, you have to replace it anyways. Not very
constructive.

Suggest you weigh the parts and compare to others known-good.

If in doubt, replace anyways.

Drying out is the expected end of life of an electrolytic, which may
have a design life as low as 200hours at it's maximum ratings.

Consumer equipment is not normally expected to be operated under worst
case conditions - units that are will age sooner.

Sometimes equipment may be accidentally plugged into an inappropriate
source, or left to run for long periods, unattended, in fault-like
load conditions ie into shorts, on top of heaters, under a deluge of
soap suds, etc etc.

How old was the unit?

RL