I'm not calling any individual "dumb" but I do find it interesting that my method of proactive capacitor replacement is under constant scrutiny. And in fact it's hypocrisy. How so? What is the first thing 99% of techs/engineers do when confronted with vintage audio equipment? That's right....100% of capacitor replacement without question (except mica's and ceramic's). So why should our vintage test equipment be treated any differently? Don't we value it as much as the audio stuff? Well this boy does.
Well, that pool of enthusiasts has a much higher voodoo promulgating fuckwit : Actual Tech ratio than our little enclave of TE enthusiasts, so one could easily argue that their application of the scattergun approach is more "change parts and hope you hit the broad side of a barn" technique rather than "diagnose like you know what you're doing and fix what's actually broken".
That said... I've seen too many cases of scattergun approach fixing things you didn't even know were wrong (noisy trace, poor clarity, marginal brightness on screens and displays) to discount it so foolishly. I see it more as a first diagnostic step once gear reaches drinking age.
If it's old enough to qualify for a AARP card, it has been running on borrowed time for decades; and again, just because "it works" doesn't mean it's really working correctly. ![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
Electrons are finicky things... they're lazy, but they do love to make trouble.
Freshening up the capacitors puts young constables with feet on the ground back into that mix. ![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
mnem
9. Capacitors are Murphy's footsoldiers.
On the capacitors, I'm sort of on the fence with this once. I work on the following replacement principle, objectively only:
1. Likely to blow up in your face or burn your house down (RIFAs, Schaffner filters)
2. Likely to cause secondary damage when it fails (some electrolytics, tantalums)
3. Likely to cause functional issues (some electrolytics, some paper/wax capacitors, some HV capacitors)
4. Likely to be difficult to replace later while you've got the thing in pieces anyway (anything on inspection)
Shotgunning them is expensive and in some cases extremely difficult to do without causing further damage to the item in question. Secondarily you risk causing more problems through unexpected side effects, different component properties (consider the much lower ESR of most modern electrolytics etc). Ergo make rational, objective steps only. About 50% of the time that does result in shotgunning but should not be confused with a blanket shottgunning policy.