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#1
05-17-2011, 04:51 PM
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1950's DuMont Teleset Model RA-170
Here is a DuMont black and white set I got this weekend at an estate sale. I didn't want to undo the ratchet straps as it still needs to be taken to my building in downtown Midland. It was nearer to bring it home first so it is still on the trailer. This is still a fairly high-performance set with 4 IF stages. The CRT is a 21FP4A, it looks fairly deep, is this a 70 degree CRT?
I'll show the front once I get it unloaded. Also I got a late 60's Motorola 20" or so color tube type table model which was still hooked up in a built in cabinet in a billiards room. 
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#3
05-17-2011, 05:09 PM
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The 21FP4 is a self-focus 70 degree CRT. It has a cylindrical face.
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#4
05-20-2011, 06:47 PM
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Chad, first, congradulations on a decent find. in the area where i live, when i was collecting sets, i could find just about every brand but Dumont. yours is in amazingly good shape considering the age.
i saw the you-tube video that you posted with the rejuvenator connected. in the video, you stated that you could not get it to rejuvenate or get any kind of emission during the test. allthough you gave the filament plenty of warmup time. i also noticed that there was no crt "brightener" attached to the tube on the first video that you took of the set. to me, that indicates that the tube was was not killed by the brightener. the only conclusion that i could come up with is that someone in the past killed the crt by going "overboard" with their rejuvenator, OR, one (or more) of the pins on the crt plug on the neck of the tube is making a bad connection. the best thing to do (before giving up on the tube entirely) is to heat the pins on the crt plug with a soldering gun. that might be where the problem is. i run accross this same problem on a set that i restored years ago. the tube almost got sent to the trash, but as a last resort, i tried heating the pins up & found that the tube was pretty healthy.
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#5
05-20-2011, 08:30 PM
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Your kitty has a very fluffy tail. Over in AudioKarma, there's a very long thread about cats and audio equipment. http://www.audiokarma.org/forums/sho...d.php?t=193866 Maybe a thread on pictures of cats on TV sets would be in order.
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#6
05-21-2011, 05:39 AM
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The cat always is interested in things we're working on!
I tried re-flowing the solder on the pins of the CRT but no luck. The weird thing is, is that it did show some emission for a few seconds several times when the tester was first connected and I turned the filament voltage up to 9 volts. When the filament voltage was kept at 6.3, no emission. This only occured 2 or 3 times when the CRT tester was turned on after leaving it off several minutes. After these few times, it never showed emission again, and when it did it was only for a few seconds. I maybe better check my tester again with a known good CRT but it seemed to give legitimate readings on some color CRT's several months ago. The filament on the DuMont CRT is still working but still no emission.
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#7
05-21-2011, 06:05 AM
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Try cooking the CRT heater at 8 volts or so for several hours. I've heard they can sometimes come up after being asleep for decades.
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Reece Perfection is hard to reach with a screwdriver.
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#8
05-21-2011, 02:56 PM
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Quote:
Quote:
one other thing that i would like to suggest is that since you are working on these vintage sets is to get a rejuvenator from that era, like a B+K model 440 CT. that works the best on them old tubes. i happened to find out a long time ago that the rejuvenators that were made in the 70's - 80's did not do a very good job of rejuvenating the old type of crts like the one that you are dealing with now. in fact, on some vintage crts they would not rejuvenate at all with the modern rejuvenator. that is why i kept this old B+K & refurbished it, it would do the job that the other one would not.
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