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.

bryanska wrote:

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.

It's not a leak. The damn thing is 'worn out' !

Just replace it.

And yes it would have made a hum too.

Graham

"bryanska" wrote in
ups.com:

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.

It's not a good idea to dissect electrolytic capactiors. They have nasty
chemicals inside them.

It's not a good idea to dissect electrolytic capactiors. They have
nasty
chemicals inside them.

Still, if the center is lighter-colored than the outer layers, is this
a symptom of a leaky cap?

Jim Land wrote:


It's not a good idea to dissect electrolytic capactiors. They have nasty
chemicals inside them.

Gee what is YOUR definition of "nasty chemicals" !!!
Sodium Borahydride maybe ?
Yukio YANO

bryanska wrote:
It's not a good idea to dissect electrolytic capactiors. They have
nasty

chemicals inside them.


Still, if the center is lighter-colored than the outer layers, is this
a symptom of a leaky cap?



Are we talking electrical leakage or physical electrolyte leakage? The
brown stuff could be electrolyte, or it could simply be glue used to
support the large capacitors.

Yukio YANO wrote in
news:FIUth.797812$R63.487719@pd7urf1no:

Jim Land wrote:


It's not a good idea to dissect electrolytic capactiors. They have
nasty chemicals inside them.

Gee what is YOUR definition of "nasty chemicals" !!!
Sodium Borahydride maybe ?

From Wikipedia entry on Electrolytic capacitors:

Safety

The electrolyte is usually boric acid or sodium borate in aqueous
solution together with various sugars or ethylene glycol which are added
to retard evaporation.

*** Care should be taken to avoid ingestion of or eye contact with the
electrolyte, and any areas of the body where skin contact has occurred
should be washed in good time.

*** It is important to follow safe working practice and to use
appropriate protective equipment, notably gloves and safety glasses, when
working with the electrolyte.

*** Some very old tantalum electrolytics, often called "Wet-slug",
contain the more hazardous sulfuric acid, however most of these have
corroded away by now.

(emphasis added)

I for one have grown weary of endless warnings inserted in countless
replies. Do we need
to lecture an adult about taking apart capacitors? Just offer something
constructive about his
question or stay quiet. Maybe he's a teen, so what, this is mild stuff,
not VX. Has anyone here
burned their fingers toying with capacitors as kids? Nothing happened
when I played with them.
And I had enough sense not to rub it in my eyes, and I'll bet if your
curious enough to want to take apart a
capacitor, your smart enough to not eat the stuff.

These constant warnings are distracting and paternalistic. It makes you
look like a helicopter parent, hovering about, quick
to swoop in eliminate any and all perceived hazards, but saying little
about the question.

As a concession, you can require group users to read a safety warning,
"Warning: Advise Offered On This Site
May Be Dangerous" Then we can ponder the questions and stop being
endlessly irritated. Warning: reading this post
make cause extreme mental fusing, if so, seek professional counseling,
just don't complain here.

Are we talking electrical leakage or physical electrolyte leakage? The
brown stuff could be electrolyte, or it could simply be glue used to
support the large capacitors.

The brown crust was definitely leaked. It was irregular, not completely
encircling any of the three capacitors it pooled around, and connected.

Does anyone have any thoughts to my original question? Does
lighter-colored paper in the center of the wind indicate a leak?

wrote in message
oups.com...
Are we talking electrical leakage or physical electrolyte leakage? The
brown stuff could be electrolyte, or it could simply be glue used to
support the large capacitors.

The brown crust was definitely leaked. It was irregular, not completely
encircling any of the three capacitors it pooled around, and connected.

Does anyone have any thoughts to my original question? Does
lighter-colored paper in the center of the wind indicate a leak?


Are you sure that "crust" is not just the remains of some of that dreadful
brown glue that you often find around the bottoms of such caps, originally
put there by the board manufacturer to improve the mechanical stability of
the caps ?

Arfa

"distar97" wrote in message
oups.com...
I for one have grown weary of endless warnings inserted in countless
replies. Do we need
to lecture an adult about taking apart capacitors? Just offer something
constructive about his
question or stay quiet. Maybe he's a teen, so what, this is mild stuff,
not VX. Has anyone here
burned their fingers toying with capacitors as kids? Nothing happened
when I played with them.
And I had enough sense not to rub it in my eyes, and I'll bet if your
curious enough to want to take apart a
capacitor, your smart enough to not eat the stuff.

These constant warnings are distracting and paternalistic. It makes you
look like a helicopter parent, hovering about, quick
to swoop in eliminate any and all perceived hazards, but saying little
about the question.

As a concession, you can require group users to read a safety warning,
"Warning: Advise Offered On This Site
May Be Dangerous" Then we can ponder the questions and stop being
endlessly irritated. Warning: reading this post
make cause extreme mental fusing, if so, seek professional counseling,
just don't complain here.


So what's your next safe project ? Sawing the tops off of RF power
transistors ... ?? d;~}

Arfa

wrote in news:1169761239.289133.179680
@s48g2000cws.googlegroups.com:

Are we talking electrical leakage or physical electrolyte leakage? The
brown stuff could be electrolyte, or it could simply be glue used to
support the large capacitors.

The brown crust was definitely leaked. It was irregular, not completely
encircling any of the three capacitors it pooled around, and connected.

Does anyone have any thoughts to my original question? Does
lighter-colored paper in the center of the wind indicate a leak?


no, it just indicates a higher degree of reflectivity.

Whether it leaked or not does not particularly matter if it was bad, though
the brown crust was likely glue.

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Are you sure that "crust" is not just the remains of some of that dreadful
brown glue that you often find around the bottoms of such caps, originally
put there by the board manufacturer to improve the mechanical stability of
the caps ?

Arfa

YES.

Whether it leaked or not does not particularly matter if it was bad, though
the brown crust was likely glue.

Ya know what? I am going to post a picture of the damn board, and the
capacitor.

OK, on Flickr are several pictures.

Included is the best picture I could take of the board. With the two
large caps being new, they mostly covered up the brown crust. It's now
barely visible.

Also included are pics of the top and bottom of the cap in question.

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

"bryanska" wrote in news:1169777565.861550.286390
@v33g2000cwv.googlegroups.com:

OK, on Flickr are several pictures.

Included is the best picture I could take of the board. With the two
large caps being new, they mostly covered up the brown crust. It's now
barely visible.

Also included are pics of the top and bottom of the cap in question.

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


Hmm, looks like old glue...

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"me" wrote in message
...
"bryanska" wrote in news:1169777565.861550.286390
@v33g2000cwv.googlegroups.com:

OK, on Flickr are several pictures.

Included is the best picture I could take of the board. With the two
large caps being new, they mostly covered up the brown crust. It's now
barely visible.

Also included are pics of the top and bottom of the cap in question.

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


Hmm, looks like old glue...

I have to say that it does to me as well. Remains of leaking electrolyte
tends to go crystalline as it dries out, and is usually a very light colour.
I repair hifi all day every day, and it is very common to find a brown crust
randomly distributed around the bottoms of the caps, and it *is normally*
the remains of a particular glue that the manufacturers squirt around, and
which is well known in the trade for its deteriorating properties, over a
few years. Some varieties of it even become mildly conductive, and can wreak
havoc with some high voltage sections of TV sets. Assuming that you are
correct however, and it is the remains of leaked electrolyte, you should not
have fitted new caps on top of it. Any electrolyte leakage onto a board,
should be scrupulously cleaned off first.

Arfa