Sealing Filter caps?

[SwizzyMan]

Hello all!

Ive had this idea in my head for a while now... I thought since it is usually uncommon to come by 3 good filter caps that I could maybe seal the terminal holes with silicone sealant to prevent the remaining electrolyte paste from drying out thus increasing the cap's life. Could this be done?

[Kamakiri]

Wouldn't really be worth the attempt IMO. Caps are cheap enough to replace.....

[bandersen]

I believe the electrolyte breaks down chemically even if it doesn't dry out.

[NoPegs]

For some values you can use film caps as replacement, if operated within design limits they should last many decades, or at the very least should outlast a high-quality modern electrolytic.

[Olorin67]

those holes might be safety vents to keep them from blowing up if they fail.

[Kamakiri]

Originally Posted by NoPegs

For some values you can use film caps as replacement, if operated within design limits they should last many decades, or at the very least should outlast a high-quality modern electrolytic.

Really? Never heard that before.....

They're about 10x the price.....

[SwizzyMan]

Oh ok then, I will replace mine when they start to become an issue as they are barely leaky.

[zeno]

Originally Posted by Olorin67

those holes might be safety vents to keep them from blowing up if they fail.

Which is why I would do it & hook it up backwards !

73 Zeno

[Gregb]

Originally Posted by SwizzyMan

Oh ok then, I will replace mine when they start to become an issue as they are barely leaky.

I would still consider changing them before you have an issue. A fellow collector friend of mine had an AM/FM radio that had what he considered a good electrolytic and it went from working just fine to smoking the power transformer in just a few minutes. He told me it was playing just fine with no hum and he went to get a coffee and was gone just a few minutes. Upon his return there was no sound at all and smoke was pouring out of the radio.
If you don't change those caps don't ever walk away from it when its powered up. Its amazing how fast they go south when they fail and even being there you may not be able to prevent damage when it does fail.

Gregb

[Jon A.]

Originally Posted by zeno

Which is why I would do it & hook it up backwards !

73 Zeno

I have a huge one that came out of a mid-70s Hitachi that's probably no good anyway...

[Electronic M]

Originally Posted by Gregb

I would still consider changing them before you have an issue. A fellow collector friend of mine had an AM/FM radio that had what he considered a good electrolytic and it went from working just fine to smoking the power transformer in just a few minutes. He told me it was playing just fine with no hum and he went to get a coffee and was gone just a few minutes. Upon his return there was no sound at all and smoke was pouring out of the radio.
If you don't change those caps don't ever walk away from it when its powered up. Its amazing how fast they go south when they fail and even being there you may not be able to prevent damage when it does fail.

Gregb

Did he ever test that cap for leakage at rated voltage? Hum is often from the cap going open rather than leaky. If it is still filtering ripple, but leaking and taxing the supply it may be hard to notice the problem until other stuff fails. I'd recommend adding a B+ fuse between the rectifier and first cap if you keep the originals to reduce chances of blowing a rect. tube or worse.

[Gregb]

I don't know exactly what he did to determine the cap was "Good". I have repaired a number of radios over the years that where "just fine" and all of a sudden there was smoke. Don't trust those old filter caps, they are a ticking time bomb.

Gregb