Big 'audio' capacitor source

[SeanB]

Running out of electrolyte and going dry. Normally you would find the interior full of a very thick liquid electrolyte but with time the water making it up diffuses out of the seals and the self healing of the oxide film breaks the water into hydrogen and oxygen which diffuses out the seals as well.

[calexanian]

For important stuff i know I don't ever want to go into again I will re form the caps and monitor current. It really does make a difference. This is particularly useful when you are operating a cap at WELL BELOW its voltage as it may never form completely in use. Don't assume it was properly formed when made. Cap manufacturers are notorious for testing at low voltage and never really giving a proper forming and power soak.

[Rufus]

Running out of electrolyte and going dry.

So I weighed them, the 'bad' one was 76.9g the other 77.4g.

I opened up the other one and it has just as must free space in the can. It didn't rattle because the winding was better wedged against the end of the can. These are 9 years old and don't run particularly hot.

Wish I had noticed earlier and weighed the replacements.

[calexanian]

Weighing them is not really a good method because the electrolyte these days is in gel form and the tightness of the wrap has a lot to do with how much is there.. electrical tests like monitoring ripple voltage and current, leakage, capacitance, etc etc etc, are better indicators of cap health. There are even "DRY" electrolytic caps which is not really accurate, but how they were marketed. I think they are all gone now..

[wraper]

Looks perfectly good inside. Wet paper, liquid will come out if you squeeze that paper. Are you sure it was really bulging? I have some new big ELNA caps and top of them is not completely flat, a little bit bulging, ~1mm higher at the center compared to the sides..