Rejuvenation of the CRT in a 15" GE B&W TV, using a B&K 470 CRT tester/rejuvenator
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- Опубликовано: 12 сен 2024
- I was recently given a late '70's 15" GE B&W TV that worked; but, it took a long time for the CRT to warm up enough to produce an acceptable picture. When a CRT starts to weaken, the cathode becomes contaminated; thus, causing reduced electron emission from the cathode. Over time, the condition will become worse until the CRT becomes too weak to produce an acceptable picture. In fact, I've seen some CRT's that were so weak that they'd barely light up in a dark room.
The only permanent fix for this problem is to replace the tired CRT with a good one. It may not always be practical to spend the high cost for a new CRT and, in some cases, a good tube may be impossible to find. That's where rejuvenation comes in.
During the early days of TV, companies started to make CRT testers that would not only test a tube for emission and shorts; but, would also rejuvenate a weak tube. The way this works is by applying a high voltage between the cathode and G1 electrodes of the CRT. The resulting arc between the two elements will blow off the contamination on the cathode; thus, exposing more "good" surface, which will increase electron emission. Unfortunately, these older rejuvenators didn't have any type of current limiting circuitry in rejuvenation mode and the result was often a cathode that was not only stripped of it's contamination; but, it's usable material. Often, the CRT would be worse after rejuvenation than before. My first CRT tester was a mid '60's era B&K model 465. It was a good tester for testing older color and B&W tubes; but, it's rejuvenation process was risky. I had luck with rejuvenating quite a few B&W tubes with it; but, I also blew up a lot of tubes with it (no matter how careful I was).
By the mid-to-late '70's, manufacturers started to offer more advanced CRT rejuvenators that offered current limiting circuitry on the rejuvenate function that resulted in less danger of ruining a CRT from rejuvenation. The Sencore CR70 and the B&K models 467, 470, 480, and 490 fall into this category. The above mentioned testers will also easily test more recent CRT's, as well as older tubes.
I've been using the newer B&K testers since the mid '90's and I've rejuvenated a boatload of newer and older CRT's, both color and B&W, with it. And, I've had very few tubes that were ruined by these newer testers.
Just remember that rejuvenation is a temporary fix and it's hard to determine how long the tube will hold up. I've rejuvenated tubes that died a day later and I've had tubes that lasted for several years. Some tubes will be totally worn out and no amount of rejuvenation will help them, no matter what tester is used.
If you plan to get into the hobby of restoring vintage TV's, I'd highly recommend getting a good CRT tester. When I get a vintage TV, the first thing I do is check the CRT to make sure it's good. There's no need to overhaul a chassis just to find out that the CRT is a dud and can't be saved.
When these testers were new, they cost several hundred dollars and some even crossed the thousand dollar line. Since the advent of flat panel HDTV's, the demand for mainstream CRT TV reapir has dropped off, and, as a result, used CRT testers can often be bought for well under $100. Check ham and antique radio swapmeets, local TV shops, and ebay.
Again, get a later model one from the late '70's or newer because these will more readily check the later CRT's and the rejuvenate function is more reliable. The older models are limited to what tubes they can easily check and the "brute force" method of rejuvenation can often cause more harm than good.
![How to Rejuvenate an arcade CRT monitor [B&K 467]](http://i.ytimg.com/vi/nWqqB_OnYzE/mqdefault.jpg)
Nice video. I've also seen B&W CRT's go negative when you turn up the brightness. This happened on a 1959 Zenith B&W 17" set i had when I was in high school. I replaced it with a rebuilt tube and the set worked fine until 1977 when I bought a color set and brought the perfectly working Zenith to the dump. What a HUGE mistake I made that I regret to this day.
I enjoyed this video, very nice to see this again. I 'm a retired RTV engineer and reguvenated hundreds of CRT colour tubes as well as black one's. Ik still have my simple reguvenation machine the König TR 450 of German make, bought in 1980 and still and still working without any error. Pitty that the CRT has gone......
I USED to have this EXACT CRT checker/rejuvenator...lost it when my "friend" auctioned off all my stuff! Thanks for the video, brings back memories!
I feel for ya mate
I've got a b&k as well, paid 10 bucks. Nice machine there. Liked the video!
I picked up one of these at a yard sale really cheap one day, I used to have a Sencore CR-70 which was a really good tester too. I always did the clean and balance several times first.
Very nice!
You prolly dont give a shit but if you are stoned like me during the covid times then you can stream all the new series on InstaFlixxer. Have been streaming with my gf for the last weeks =)
@Cayden Decker Definitely, I have been using instaflixxer for since november myself :)
@Cayden Decker yea, been watching on InstaFlixxer for months myself :)
I was given an old B&K Cathode Rejuvenator Tester some 30 years ago.It was in an old portable phonograph case.
This set has a great picture.
Thank you, this helped with the 467 saga I was having. Was stuck on the "One division, one division". What were they saying? I get it now.
If a CRT that was otherwise good has been sitting unused for decades, they can become weak. Often, running them at 2-3 volts higher than their normal filament voltage rating will wake them up. This process may take anywhere between a few minutes and several hours to take effect. Also, they used to make CRT brighteners that were designed to plug in between the TV's CRT socket and the CRT. These devices raised the filament voltage; thus, making the cathode hotter & producing more electrons.
Very good video. I gave it a LIKE. What does the G1 elemnt do and how much is the voltage on it ?
I remember having one of these tvs back in the early 90s. The tube got weak on it but I didn't rejuvinate it. Have the same tester as yours.
Love your channel. would rejuvenation work for a monochrome monitor? we have a cnc mill at work with a dim monitor. in fact we have to turn out the lights to plot out a program. its yellow monochrome if that makes a difference. the mill is a hurco cnc mill from the early 80s.
btw it uses to monitors sideby side.
billybonewhacker You can try...
Thank you for explaining how rejuvenation was accomplished. I assumed high voltage, but to drive contaminents to the getter and repel contaminents off themitter. How did brighteners work? Increase filament voltage to make cathode hotter?
That's a Great TV
Great video and explanation. Thank you
I used to have a B&K 445, when I was doing TV service, but this unit had no current limiting. I never smoked a CRT with it, but I saw the potential for it happening. Unfortunately, I left it at a customer's premises, and it strangely disappeared within one day when I remembered where i had left it. I need to start looking around for a Sencore CR70 which is the particular one I favor. It would be risky to try & rejuvenate a color "roundie" 21FBP22/JP22 etc with an old B&K...those tubes are getting harder to find. My main line of work besides being a DJ on the weekends is, Amplifier repairs & pro audio equipment repairs..I repair a lot of guitar amplifiers, and sound reenforcement power amps. I'm the local tube specialist in my area...kids nowadays coming out of electronics schools don't seem to have a clue about vacuum tubes :) The technology is still popular and will be around for a long time comin' Tube theory should still be taught in the schools.
Awesome!
Oh, thanks i might try that on a tv that i have that it seems to have a dim picture, since i dont' have a crt rejuvenator.
thanks for the reply.
Probably the reason why Sears disabled the rejuvenator portion of your tester was that Sears didn't want to wake up a weak tube, just sell the customer a new set!
radiotvphononut
: My two Philco Seventeener III's just started acting up. One lost all picture and raster while I was adjusting the set after a cap replacement. Has good sound and had a great bright picture and nearly instant video. The other suddenly started acting up - the high voltage takes nearly 20 seconds to come up and the screen takes that long to produce a picture. IT is plenty bright just terribly SLOW to come up. Any ideas?? These two sets are beautiful, but I am pulling my hair out. I have a SUPER MACK tester - but am now afraid to test the tubes based on your comments about destroying the tubes...
I bet Sears disabled the rejuvenation function to keep the techs from blowing the CRT up and having an irate customer on their hands.
Maybe but I had a tech tell me you aren't allowed to charge for that at least not in Calif.
What can be done about heater/cathode shorts in Trinitron tubes ? I have 2 identical Sony TV's with this problem, if the shorts can be blown out, how long will they stay good for ?
I have a vintage Motorola set that uses a 17HP4 CRT. I ended up having to replace the CRT as the one that was in the set was so bad. I could only see it in a dark room and it had a heater to cathode short. The CRT was so gone it wouldn't even register on the CRT tester and doing a rejuv had no effect on it.
ESDI80 Nothing lasts forever...
any way to get in touch you with, to talk about testing my CRTs? with a B and K 470 tester.
I have the 470 Picture Tube tester/ rejuvenator like new! I have no use for it if anyone is wanting to buy one?
Amigo, esta TV está com a imagem perfeita. Parabéns! Rio Brasil
RADIOTVPHONENUT,
Is the CRT rejuevenator adding and injecting more Electrons into the RGB ray gun?
What is the CRT rejuevenator doing to the monitors neck circuit board and tube?
It's pulsing high voltage between the cathode and G1, which blasts off junk from the cathode and allows more electrons to be emitted.
@@TCGProductions03 Ok thanks
When adjusting the B+ voltage why do you need to adjust the brightness trim pot to maximum to get the correct B+ voltage?
@@billwilliams6338 The B+ will be lowest when the brightness is at it's highest. Setting the B+ with maximum brightness will ensure that the set continues to work properly, no matter what the CRT is displaying.
@@TCGProductions03, thanks for the help
What I'm confused about is what does the brightness current and voltage have to do with the B+ voltage?
The Brightness is controlling what in the TV tube and circuits?
what happens if you just increase the voltage of the heater, does that help?.
Will this work on a crt computer monitor?
i have a Bk 466, please, tell me that it isn't so bad... you recommend me something?... any adaptation for better performance ? Thanks
Where can I buy a CRT Tester? This looks like a useful machine and are they expensive?
NotThatDisgusted Check EBay... they have all kinds of stuff.
Thank you for the advice I will check.
NotThatDisgusted I have one I'd sale?
Do they still sell cry tubes any. more. Anyone
IDK about TV shops still using these, I don't know of ANY around my area that will even work on a CRT anything let along be using any type of tube testing gear and those shops are very few and far between. I think I am the only person in a 100 mile radius that owns a tube tester and I work on 2-way radios and related equipment
Which is why all picture tubes black and white and early colour tubes all the way up to the late 80's (and possibly early 90's well i would save) need saving! or rejuvination which is unreliable
Sony T I have 2 trinitron tube that have green cathode-heater short, can they be fixed, if so will they stay fixed
Im glad they stopped making crt sets, they were dangerous, heavy and a pain in the ass.
Throw it away its not needed for anything.
belly tripper Im not a crt hater as ive got 2 crts in my room i mean why does he need a black and white one
some of us folks collect these