21fbp22 crt life - Videokarma.org TV - Video

timmy · #1 03-17-2013, 07:45 AM

hi all, just a curious question about the 21fb or 21fj crts weather they are original or the replacements of the 1980s , im not sure what the other one was it starts with 19h i think. is there a way to determine the life left in these crts based upon the reading of emission given by the tester itself ? the bk440 i have would show 300 or higher on the scale where 200 is said to be weak. the mistake i made was i never did warm the tubes up as they say to do for a few minutes i just plugged it in and got the reading and i was done. it seemed at the time i was more determined to get to the chassis as long as i had a decent reading on the tester. besides the socalled life test and im not so sure this is accurate but would the emission reading mean anything as far as life goes.

miniman82 · #2 03-17-2013, 08:17 AM

Emission merely shows the amount of electrons given of by the cathode, in order to get some idea of the life left you do the 'life test'. For testers without this function, simply turn down the filament voltage to 5 or so. If the meter dips into the red, you'll know it's got a lot of hours on it but will still likely give a decent picture. Most of the tubes I have retain full emission all the way down to 4 volts on the heaters, meaning they have seen very little use. It takes a little bit of experience to get a feel for how your meter will respond to good and bad tubes, but once you test a few of them you get the hang of it. Take a good one and a weak one, play with the filament voltage while reading emission on the scale. You'll quickly see the difference in the how needle reacts.

timmy · #3 03-17-2013, 03:02 PM

well that makes sence ill have to try that as i have 2 sets that the crts were replaced in 1982 which still dont make them better then the ones from the 60s i know just depends on hours. ill try that with heater voltage, thanks.

holmesuser01 · #4 03-17-2013, 04:26 PM

I've seen CRT testers that didn't have enough current available to properly light the 3 filaments in a roundie tube, so the tubes would read as weak.

I've got one tube that reads low on all 3 guns, has a decent life test reading, and tracks fine. Rebuilt tube with Magnavox's name on the label.

timmy · #5 03-18-2013, 11:54 AM

so i guess the best way is to test it at 5 volts and use the life test, but even if this shows that its been used or alot of hours on the tube still dont really tell how long it may last. but what the heck i run my roundies sometimes once a week and for only maybe 20 minutes at a time just to not have them sit around and keep the caps alive.

holmesuser01 · #6 03-18-2013, 11:58 AM

I'd test them at 6.3v then lower the filament to 5 and see if the needle drops.

Remember, these sets were (in the case of my house growing up) left ON from early in the morning, until we went to bed. I know people that sleep with the dang things turned on.

Running your sets just a few minutes at a time is not going to kill them.

miniman82 · #7 03-18-2013, 05:48 PM

It's better to let them run for at least 10 minutes, so things have a chance to warm up completely. My personal opinion is that it helps keep moisture out of critical parts like the flyback, and the last thing we need to hear about is another bad FBX.

holmesuser01 · #8 03-18-2013, 06:02 PM

Quote:

Originally Posted by miniman82

It's better to let them run for at least 10 minutes, so things have a chance to warm up completely. My personal opinion is that it helps keep moisture out of critical parts like the flyback, and the last thing we need to hear about is another bad FBX.

Yes, let it get warmed up. I was drunk when I posted before, apparently.