(WARNING BURNED SKIN)Don’t bypass capacitors

Are modern capacitors made better than the ones in old tube equipment? Is the shelf life longer?
At the rate the things are advancing in the RC brushless motor field, these only need to live for a few years before the controller will be replaced due to obsolescence, or the need to have the latest and greatest.

In the RC club I belong to I get picked on for running a 12 year old transmiter.
You have asked a couple of excellent questions. The first is if the quality is good, I believe that the caps are better. The second I have no answer. From my 40+years of experience in electronics, electrolytic capacitors can be a finicky component. I have tube equipment that go back to late sixties that never had any service and work fine. And then there were new solid state amps that the cap blew it's top. The bottom line is quality components and good design. It would not surprise me my friend, if you get another 12 years out of your old transmitter.
 
You guys made me curious enough to see how they are made. I found this: http://www.rubycon.co.jp/de/products/alumi/pdf/Process.pdf

I can see plenty of opportunity for poor materials or poor manufacturing processes to cause problems. Electrolytic capacitors are old enough tech that I suspect it's more about the manufacturer's quality processes than modern fab techniques vs. old.

The "we know more now" concept cuts both ways: it's pretty common to see people getting 200K and 300K miles or more out of a modern engine, but there sure are a lot more things that can go wrong now (sometimes catastrophically) than with an old big-block V8. Knowing more makes us push things further, often with tighter tolerances and margins, cheaper materials, and shorter supported lifetimes. This is particularly true for replace-on-failure components.
 
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