Quote:
Originally Posted by Kevin Kuehn
I have a B&K 466 that seems to work ok, I've rejuvenated a couple tubes succesfully with it. Now I'm curious what shops used back in the 50's to get the job done, or did they only sell new or rebuilt tubes when they got weak?
Kevin
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I knew a guy who ran a TV/radio service shop from the late '40's until 1973. He once told me that he used various B&K models, including the popular blue cased 465. He said that when he ran into a weak tube, he would try to talk the customer into buying a new tube (assuming the TV was worth a new tube). He would also add that there was a chance that he could rejuvenate the old tube; but, chances were good that it wouldn't last long and there was a chance that rejuvenation might make the tube look worse than before. If the customer didn't want to spring for a new CRT and if they were willing to take a chance, he'd rejuvenate the tube. He said that the results varied from making the tube brighter for a few hours up to a few months. And, there were those tubes that rejuvenation either didn't help at all or made them worse. If the customer later wanted a new CRT, he would apply the rejuvenation cost towards a new tube.
My first CRT tester was a B&K 465 that had three levels of cathode stripping (oops, I meant rejuvenation). On the lowest setting, I had some luck at bringing back weak B&W tubes. Usually, if the lowest setting didn't do it, you could forget it. And, I never had much luck with rejuvenating color tubes with this tester.
I think where a lot of shops made their mistake was thinking "more is better". Instead of starting out with the lowest form of rejuvenation possible, they'd flip the rejuvenator to "high" and end up burning up a tube that could have probably been saved had they used caution. Once, I loaned my 465 to a TV repairman friend, who didn't have a CRT tester at the time. He wanted to rejuvenate a '70's delta gun color tube. Despite my words of warning, he flipped the tester on the highest level of rejuvenation and pressed the rejuvenate button about 6 times. Needless to say, he ended up putting another tube in that set. When I rejuvenated a tube with this tester, I set it on the lowest form of rejuvenation and hit the button once, for a fraction of a second. Then, I'd recheck the emission level.
I'n the mid '90's, I bought a newer B&K 470 and I have rejuvenated all sorts of tubes with it. I'd say that it's helped 95% of the CRT's that needed rejuvenation and I don't think I've ever had a CRT that was worse after rejuvenation. The other 5% of the CRT's that it didn't help were usually either worn out or poor quality ('90's era Zenith tubes) to begin with.
Even on the B&K 470, I start out using the "clean and balance" function. Usually, this will do the trick. If it does not, I move to the rejuvenate function. And, I can usually tell if the CRT will hold up or not by how long the meter pointer stays up. When I press the rejuvenate button, if the meter rises a small amount and immediately falls back down, the CRT probably won't hold up. If the pointer rises towards the middle or top of the scale and stays there for several seconds before slowly dropping back down, the tube will probably hold up.