DIYbanter - View Single Post - Why should someone replace ALL the capacitors on old Tube equipment?

Foxs Mercantile

On 2/4/2017 4:28 AM, wrote:
Lets take my Hallicrafters SX-99 (which I paid for but don't have
yet). That radio is 62 years old. (made in 1955). The seller said
it works fine, (and I was sent a video of it working. I did detect
a very slight hum. (But the video's audio is not the greatest).

However, this is a working radio. I ask myself if I really want to
replace all the other (small) caps. [Then I say to myself.... if it
works, dont fix it].

To quote a good friend of mine, "There are only two kinds of paper
dielectric capacitors. Those that are bad, and those that are going
to be bad."

Where I do NOT feel comfortable changing them, are in all RF and IF
stages.

The paper caps in the RF and IF stages are bypassing and coupling
capacitors. They need to be changed as well.

I answer myself "Probably not".... (As long as the radio is working
well, don't screw up a good thing.... Then too, if the caps in those
circuits are .05 or .003, I WANT a .05, not a .047. (And it seems
that .05 is no longer made).

"Working" is a subjective thing. Known failure prone parts are just
a time bomb waiting to convert working to not working. And possibly
causing collateral damage when they fail.

Back then, they liked "round numbers." Then the industry standardized
on incremental changes.
As a matter of course, .02 now is .022, .03 is .033 and .05 is .047.
Unless you're playing with tuned audio filters, the difference is
statistically zero.

--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com