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

Benderthe.evilrobot

wrote in message
...
On Thu, 2 Feb 2017 15:38:45 -0600, Foxs Mercantile
wrote:

On 2/2/2017 2:53 PM, wrote:
Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

Most "old" radios are from 1930-1960.
That makes them 87-57 years old.

Manufacturing has changed a lot.

I change all the caps simply because I don't waste my time
"troubleshooting" bad caps.
Bad caps can cause collateral damage.
Why risk it for the cost (low) of replacement parts?

Old electrolytic filter caps dry out.
It's a fools game to waste time trying to reform them.
Paper dielectric capacitor absorb moisture and that
combines with the acids in the paper and cause them to fail.

For the most part, mica, silver dipped mica and ceramic
capacitors are very reliable. The band ones, you can find
AFTER you've replaced the usual suspects and can actually
trouble shoot the radio rather than running around in circles
chasing known bad parts.

Yes, I've had to replace the occasional vacuum tube, or found
an open coil, but for the most part 99% of the radios I've
worked on, worked to a fashion by just replacing known bad
parts. I.e. Paper and electrolytic capacitors.

I'm 66 years old. According to my doctor, I dont have any bad
capacitors, (just arthritis).

Seriously, I wonder what the life expectancy is for the new caps
(meaning the replacements for the wax coated paper caps. ???)

And what are these newer ones made from?

I know the mica and ceramic caps are reliable and last almost forever.

I've seen loads of ceramic caps fail - but mostly in TV horizontal scan
sections where the frequency is over 15kHz and high voltage pulse
conditions.

This got worse with ever increasing PC monitor resolutions.

AFAICR; mica caps were pretty reliable - in most of the places I found them,
they were used for precision and a specific tempco.