Weak CRT?

[Jonathan]

I'm excited about the roundie I'm getting from the west coast, but what happens if the CRT really does have weak emission? Weak emission or weak electron guns, what can I do to save it if this is the problem?

Thanks.

Jonathan

Most (all?) picture tube testers have a rejuvenate function which basically blasts a higher than normal voltage for a limited time which may bring the tube back to life.....although this can shorten the useful overall life of the tube. But if it's already funky then you really don't have too much to lose. Ya know? Am sure others with a lot more knowledge about this will pipe up shortly and add details.

Anthony

[frenchy]

I would only start worrying about this after you get it and can test the tube, and even then just testing it is not going to prove it one way or the other that you will or won't have a serviceable picture, as long as you don't have a drastic problem like shorts in the guns, something major like that. Besides the rejuvenation, a filament 'booster' device that plugs in between the picture tube and it's connector is another option. (easy to find on ebay etc.) They only worked for a while before the tube finally gave out back in the old days, but I would think with such low useage these old sets get now being in collections it is probably an excellent option if it does some good.
Sometimes even shorts in the guns can be 'zapped' out with a jolt of high voltage if it's a piece of internal dust or debris that is causing the short.

[yagosaga]

Originally Posted by Jonathan

I'm excited about the roundie I'm getting from the west coast, but what happens if the CRT really does have weak emission? Weak emission or weak electron guns, what can I do to save it if this is the problem?

Don't worry before you had done the first test. Try to make a screenshot for us. Ask for tv dealer for a crt meter to test the crt.

[oldtvman]

before condemming the crt, check the resistors and caps around the drive circuits, they can exhibit problems that can mirror problems similar to a weak crt, dont push the rejuvenate button just yet, some of those old testers can actually cause more harm than good, the bk 467 was one of the very best crt testers we used.

[Charlie]

Don't forget... before attempting to press the magic button on your rejuvenator, you might be able to brighten your CRT up simply by cranking the heater voltage up to 8 volts for a while.

In the past, i've noticed emissions on the meter coming up into the green fairly fast when switching from 6 to 8 volts... say within 5 to 10 seconds. In this particular case, it seems that the crt will turn out good after leaving it at 8 volts for a while... say 30 minutes to an hour.

On other occassions, if I switch the tester from 6 to 8 volts and it the meter does everything it can to slowly crawl up into the good zone... may even fluctuate some. These particular tubes seem to not hold the better emissions once it's been on 8 volts for a while. At that time, then I might try the magic button. It may or may not work.

Using the rejuvenation button may or may not make things better. If it does, it usually seems the better results are short lived. The tube might stay brighter for a week, or maybe for a few months. Only use that feature as a last attempt to improve matters.

The above post is why I couched my earlier suggestions by saying that others would surely (please stop calling me Shirley) pipe in with more details. It's my understanding too that pressing the button is akin to launching the missiles, and not to be taken likely...not matter how tempting it may be. Unless you check out the alternatives FIRST it's best not to act like North Korea's head maniac.

Anthony

[rca2000]

One more thing, that may have been mentioned already:: if this tube has not ben on in a while, it will need to "wake up", as do most all CRT's (bw or color) after sitting for many years, without being powered. When the power is first applied to the tube, wiht a PROPERLY operatng chassis, or tester, the tube will most likely show poor, or ever very poor, emission, BUT, after running for awhile, if the guns are ok, the emission will improve, to a usable level,and STAY there, IF the crt is not really bad(which does happen sometimes, but not that often, on the old sets) Normal 6 volts is NOT always enough, to wake up a crt, 8 or so, might be needed, until the cathodes "wake up".

NOW-- Maybe someone else can explain to me, why Crt's "fall asleep" ,and exactly what elerctro-chemical change occurs, in the cathode, to cause this.

[blue_lateral]

please stop calling me Shirley

Roger, Roger. What's our vector Victor?