What should crt test values be? - Videokarma.org TV - Video

ohohyodafarted · #1 08-23-2006, 11:13 PM

I have a B&K 465 crt tester. I havent been active in vacuum tube electronics since I was in my teens 45 years ago.

I am collecting old B&W tv's with rounc crt's. I have 9 so far. The most recent is a nice DuMont 19" RA110.

My questions are this,

1. My B&K has a scale that reads from 1 to 1000 and the bad area on the meter is from 0 to 200. Good is from 200 to 1000. When a crt is new, or freshly rebuilt what should the crt tester read for emmission.

2. When I tested the 19ap4 in the DuMont it showed no emmission. I left it on the tester overnight and the next day it read about 500. It takes about 30 minutes now for the crt to slowly reach that reading. Is that a sign that the crt is no good. I have an RCA with 16gp4 that also acts like this.

Just wondering what a good crt should read. Not just a usable one, but a GOOD one that produces an excellent picture.

I recently bought a 12lp4 on e-bay for one of my sets. The seller claimed the tube was "excellent" It only reads 500 on my tester. Is that what an "excellent" tube should read? I am Holding back on giving this seller his feedback until I get an opinion as to what an "excellent" reading really is.

Thanks for your input.

Tubejunke · #2 08-29-2006, 09:09 PM

I can't directly answer your question about the tester but I can tell you that just from what you have described that your good old metal/glass crt has low emissions. I once had a Dumont with a 19AP4 and it had the very same problem. My beloved 56 Philco's 21ZP4B crt is the same way. With a brightener I get a viewable picture after 10 minutes or so. Even then it is kind of washed out. I feel your pain.

I would give someone at least two decent 50's sets and a couple of radios for one good CRT. Any offers?

***Eric H*** · #3 08-29-2006, 09:19 PM

A new tube will usually read about 600-800 on my 465.
Never seen a new tube go to 1000.

A good sign that a tube is excellent, besides the numerical reading, is how fast it gets there.
After a brief warm up it should climb quickly to it's maximum reading and stop, a slow rise indicates it's getting tired.

Your 19AP4 is tired but it could work fine with a brightener for many years of occasional use.

As for the 12LP4 I'd be happy with the 500 reading as long as it gets there quickly, if it takes 2 minutes to achieve that I'd be disappointed.

Also realize your tester might be miscalibrated, I have a B&K 466 and it generally gives slightly higher readings.

andy · #4 08-29-2006, 11:03 PM

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Charlie · #5 08-29-2006, 11:34 PM

If you get above 200 or 300 ua on your reading, you should be fine. On tubes that read low, or take a long time for a good reading, crank the heater voltage up to 8 volts for about a half-hour or so. You'll notice a higher reading on your emissions during this time. Later, after the tube has cooled down, turn the tester back on with your heater voltage set back at 6.3 volts. If there's still a good bit of life left in the tube, you should notice a satisfactory reading within 30 to 60 seconds. If it's still slow getting a good reading, your best bet is using a brightener.

Even if you get a lower reading, try running the tube first without a brightener in the set. The picture you get might be just fine. I have some sets that read low, but still produce a nice picture.

ohohyodafarted · #6 08-29-2006, 11:52 PM

Thanks Gang! Most informative. I am going to enjoy getting my 12 old roundies back into operation. I have only just begun, but I see that this forum is going to be a great source of information. Soon as I can get a chance I will make a post on the Show Us Your Sets thread" Right now they are not much to look at. They need a lot of work but here is the tally so far,
1 Hallicrafter 16", 1 Admiral 10", 1 Admiral 12", 2 Magnovox 12", 2 RCA 10", 1 RCA 16", 1 RCA 12", 1 Stewart Warner 12", 1 Crosley 10", 1 DuMont 19"

Does anyone have a good 16KP4 or 16RP4 they would like to sell??? I need it for the Hallicrafter set. Then neck of the crt was snaped off when the set was shipped to me.

Thanks for your input gang,

Bob G. in Milwaukee

Giulio Maiocco · #7 08-30-2006, 07:51 AM

Hi,

I tested the tube (MW43-64) of a friend's TV on my B&K 465, well the reading was over 1000 (the needle went slightly over the scale) quite quickly and the tester was not setted on the special measurement, so this tube should be quite good! I know that my tester works quite well as the tube mounted in one of my TV (another MW43-64) tests about 600 and gives a very good picture! Now I should see what my 27RP4 gives to me as the reading was 800...wish me luck!

Cheers

Giulio Maiocco