mean time between failure
 

How long do most black and white crt's from the 40's and 50's genrally last from when they are first turned on? and is it true that the newer crts last longer or not?

Not a scientific answer, but I seem to recall seeing the figure 10,000 hours somewhere.

"Failure" may be a little imprecise, since many picture tubes just get dimmer and dimmer rather than fail suddenly. When is a dim tube so weak that it must be replaced? Opinions might differ. The Sony color TV/monitor in my office has been played more or less daily since I bought it 26 years ago, and it still looks good to me.

Phil Nelson

The determining factor is the cathode coating, and whether it looses its ability to emit electrons over time.

I was shown a curve during my 2 week 'retreat' at RACS, which described the useful life of a cathode. It basically showed that an electron gun can be expected to have many years of useful life, provided that quality control was carried out correctly. If a tube was 'over processed' during QC, the cathode would already have experienced an undue amount of use and would already be on the 'downward slope' of it's electron emitting capability. On the other hand if a tube were 'under processed' (excluding any attempt to age the tube), the cathode would never get to it's full potential and would have to be rejected for reprocessing in the plant.

The only thing that has changed over the years is the equipment used to carry out QC on a CRT; the more accurate the testing equipment and methods used, the better you can expect the product to be. In that respect, I would think that a modern CRT could last longer than one built in the 'hit or miss' 40's or 50's. Then again people really knew what they were doing back then, so occasionally you see a used tube still perform quite well despite it's age.

With modern equipment comes modern repeatability, and in manufacturing consistency is key. The more uncontrolled variables, the high the probability of failure becomes. They didn't have computers back then...

I have observed that many 40s and 50s sets had their original picture tubes replaced within about five years. The replacement tubes seemed to last much longer. Also, keeping the brightness and constrast at moderate settings can extend the life of a picture tube. My 1949 Motorola 9VT1 is still going on a picture tube installed in 1954 although I have had to twice blast away a heater to cathode short in the 13 or so years I have had the set in operation.

As miniman82 says, it depends a lot on the particular manufacturer and how good and consistent their processing was. Lots of posts have been made here about particular brands or particular years of particular brands of color tubes that exhibited short life. Don't know if there has been any similar info on monochrome tubes, but probably not due to the people who had the experience being dead by now, plus the fact that even the better really old tubes have reached end of life anyway.

When I was at Motorola in the late 60's, their color tubes were mediocre, but Admiral's were even worse. The Motorola engineers were grumbling about how Motorola would have to eat a lot of warranty costs of CRTs that were sourced from Admiral.

My parents had a 1968 Zenith 22" black and white set. I remember in around 1971 the picture tube being replaced.

I've also noticed a lot of sets that had their crts replaced within the first 5 years. One older gentleman sold me a pair of sets he had stored away: his first TV, a '53 Silvertone, has a replacement crt that tests dead as nails. The second set is a '60 Motorola with a somewhat weak crt. That TV was replaced by a color set sometime in the mid-60s. So, he ran those sets hard and could count on killing a crt every 3-5 years. I think also of the GE console my parents bought around '80 and how many 12-18 hour days it had. No wonder that it had a bad "red smear" by the early 90s. It was no surprise when one day a light show started in the neck.

BTW Don't use a brightener. They raise heater voltage and will often 'finish off' an otherwise weak but usable tube. If I see one in a set I am being offered to -buy-, I am very wary.

My parents bought a B&W GE TV in '58 and I recall the picture was not bright from the start. I think the CRT got so dim it was replaced perhaps in warranty within a year or so. I believe some have commented on GE tubes being weak in that era.

Tell RACS to rebuild our B&W CRTs with COLOR guns... They'll last 3 TIMES longer... :D