Quote:
Originally Posted by Crist Rigott
Because you have to replace all the electrolytics and paper caps, there were like maybe 6 micas left. They have been known to got bad. So why not replace them too? There cost isn't too much either. Also it eliminates problems down the road. Say a mica still works, but then several hours it decides to quit. Then you have to go back and pull the chassis, trouble shoot the problem, replace the mica, maybe do another alignment, then put it back together. Seems the risks and rewards aren't worth NOT replacing the micas. Also when replacing the paper caps, most of the time there is a resistor on the terminal too. So you pull the cap lead off, why not the resistor too?
As far as the resistors go, what do they cost? Maybe 14 cents each? Some you have to lift 1 leg to measure. Half way to replacing it already. So it measures on the high side tolerance and you don't replace it. Same situation as a mica.
Also this is a hobby to me. I enjoy replacing those components, cleaning, painting, polishing, etc. This way, when I'm done with a restoration, most of the troublesome parts have been replaced with a modern (re: a better) component and I can expect a long life of excellent use.
I know some guys do a "restoration" by replacing just what is needed to get it going again. To me that is like putting 2 gallons in the tank when you can fill er up! But I'm not criticizing them it's just what they do. This is how I do my restorations. Everybody sees this hobby through their own set of eyes and gets out of it what they want to. Neither is right or wrong. But different approaches.
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"Another alignment"?...If you leave the original micas and resistors in the IF system it should never need an alignment after leaving the factory that made it. Micas known to go bad?...Yeah in SWEEP circuits that never need 'alignment', and aside from some early (630 era) RCAs non-sweep circuit micas are a rare exception....Changing IF micas is like swapping an engine in a GM car at 20K miles because you heard about this guy that bought a lemon that had it's block crack at 20K....Your putting a lot of time and effort into something that is a 1 in 1k issue that won't have significant odds of happening to your set for another 2-6 decades (depending on past & future storage conditions).
Resistors are a toss up I usually leave them till I've done a recap power up....Many sets are fine and have sustained years of regular use in my hands with original resistors, and often it is not worth the effort alone of changing them. Though I have had sets that spent years (decades?) outside where all resistors were off tolerance and drifty, and in that case shotgunning resistors was merited.
As for replacing just enough parts to make a set work: The merit of that depends on the age and (slightly on the) storage conditions of the set. Paper caps are like milk, film caps (such as orange drops) are like salt....Makers transitioned cap types around 1960 (there is about a 3 year margin of error by maker). Sets made before the transition need a full recap if they are to see any kind of regular duty...I can see powering up an original and if it works keeping it original and powering it up for a minute every few months to see if it still works, but expecting to last a half hour every week is unrealistic. Sets made after the transition often are somewhat immortal...They will often work as found and require approximately
the same amount of maintenance as they would have in the first 5 years of their existence....That I feel is a reasonable expectation for a set of that vintage.
To me the most fun part of the hobby (except maybe for the hunt) is troubleshooting. So if a set becomes too reliable and never needs routine service it quickly fades into the wall paper. (Also every problem you solve with a shotgun is knowledge you missed the chance to learn.) I expect my daily use sets to need help every 6 months to 3 years (and it is usually something I can fix in an evening or less), and so did their original owners...IMHO If you can* achieve better than new reliability then you loose the experience of owning a classic and may as well have a box with a LCD flat panel set in it.
*I Honestly doubt you can since heat is the enemy of parts, and modern components by and large were not designed to bake in a tube set...It may be solid for 5-7 years of use but once you've baked the new parts long enough it will slide right back down hill.