What exactly makes one CRT last forever, while another dies so young?
 

I mean, I always pick up 25-30 year old sets and they rarely ever have a weak or bad crt. I know the reasons why modern sets don't last (poor circuit engineering/build quality) but what is it that makes the newer crt's die off after 2-5 years?

poor engineering, cheap materials, poor quality control.

They are essentially designed to be throw-away items IMO.

Cheaper color guns with less material, poorer quality phosphors. It happens when the bean counters get in the way of quality.

My guess: the best crt's were what RCA & Zenith were turning out in the 70's. Japan,Inc. was putting the squeeze on them but moreso it was Korea. (with China around the corner) Money had to be cut; surveys were done showing that picture tubes were lasting longer than they "needed to" and so things were redesigned. That sure looks like what happened with Zenith, anyway. Again, just a guess. Not that long ago most color picture tubes were made in the US; I guess most of what is still being made today is sourced from China or the smaller "third world" countries. A color crt is still a complex piece of equipment. I suspect the biggest problems with tubes that don't last are cheap cathodes, skimpy guns, and impurities.

And the newer sets drive the tube right to the limit with beam current. That's probably one of the biggest reasons.

Charles

Environmental laws ruling out some durable but unhealthy phosphors and cathode coatings are another possible reason.

I´m pretty sure it would be better for the enviroment to make TVs that lasts for 30 years with some toxic materials instead of an "enviromental friendly" one which lasts for maybe 5.

Remember: we're talking about the same numbskulls who put MTBE in gasoline in the 90s, which was to clean up the air. It did. However, it has very small molecules, which leached into the ground water and spoiled the entire Santa Monica, CA well water system for decades to come, and also it ate up the rubber in car fuel systems, causing a 1000 percent increase in car fires, belching thousands of tons of cyanide gas and black smoke into the air. (source: news article quoting a State Farm Insurance statistic at the time)... Naturally they removed MTBE after the damage was done.

Charles

I have really not seen a lot of cases of bad/weak CRT's in modern sets. The only ones that really come to mind are some Sonys beginning in the early-mid 90's and the infamous Zenith bad CRT's. I don't have a lot of experience with the absolute latest sets but almost all 80's and 90's ones I have, still have good CRT's.
The era that seems to have the most weak CRT's to me seems to be late '70s or early 80's. In almost all the RCA consoles I have seen from this time period, both delta gun and inline, the CRT's are either totally weak or the red is weak.
Zenith 25" inline tubes from this time seem to be prone to weakness too.

sylvania black matrix tubes didn t last long either. both delta and inline,mid 70s to early 80s.i replaced alot of them with the 25vamp22 from the old hybrids and any zenith tube. rca s in the late 70s took a dive too.