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  #16  
Old 11-11-2013, 03:08 PM
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Testing the CRT with my Sencore CR-70 doesn't have me dancing, so far. I measure .7 ohms between pins 1 and 14, so the heaters are not completely open.

Before connecting the universal adapter to the CRT, I set the heater voltage to 6.3. When I connect the UA clips to the pins and turn on the tester, the voltage drops to around 3 volts and the CR-70 makes a high whining noise. If I disconnect a heater pin, the noise goes away and the voltage goes back to normal.

The CRT passes the H-K shorts and G1 shorts test, but the needle doesn't move at all for cutoff test or emission test. This is the same for all three guns.

Suspecting operator error, I double-checked the manual and looked at an old photo of my tester connected to the 21CYP22 in my CTC-7. With exactly the same settings, the tester worked normally and checked the emission, etc., for each gun in that tube. I even hauled the tester out to check a B/W tube, and the tester works normally.

Not sure what is going on here. For an old B/W tube, I'd just let it sit on the tester for a while, to see if it wakes up under normal or slightly elevated filament voltage. I don't see any glowing inside the base, but the base is getting warm.

Phil Nelson



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  #17  
Old 11-11-2013, 03:25 PM
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Can you actually see the heaters lit inside the neck?

Unfortunately, continuity but drawing excessive heater current and not lighting up sounds an awful lot like the tube has gone to air. Can you pull some of the neck components loose to get a look at the getter flash?
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  #18  
Old 11-11-2013, 03:35 PM
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Sounds like air. The getter is under the yoke somewhere, a slotted area around the neck provides a window to view it.
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  #19  
Old 11-11-2013, 04:48 PM
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Selenium rectifiers AND a power transformer? Usually Selenium rectifiers are used in hot chassis sets, and transformer sets have tubes like 5U4 for the power supply B+ production. Or are these seleniums used for another function?


Hopefully the CRT's vacuum hasn't leaked out.
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  #20  
Old 11-11-2013, 04:48 PM
old_coot88 old_coot88 is offline
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The base getting warm that quickly certainly points to air.

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  #21  
Old 11-11-2013, 05:14 PM
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Area inside these slots looks milky

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  #22  
Old 11-11-2013, 05:23 PM
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Quote:
Originally Posted by wa2ise View Post
Selenium rectifiers AND a power transformer?
Yes, similar to the CT-100.

Phil Nelson
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  #23  
Old 11-11-2013, 05:32 PM
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Seems like an air dud. Sorry it's gone to air.
Anyone ever install a 21CY in a CTC-4 without modifying the mask area, or other mounting hardware? I know about cutting the yoke flange when using an FB.
Kevin
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  #24  
Old 11-11-2013, 06:16 PM
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Quote:
Originally Posted by stromberg6 View Post
Seems like an air dud. Sorry it's gone to air.
Anyone ever install a 21CY in a CTC-4 without modifying the mask area, or other mounting hardware? I know about cutting the yoke flange when using an FB.
Kevin
Cutting the yoke flange for a 21FBP22?! I still entertain hope of getting a good AXP for mine so I just used a modern cup HV connector and stuck several layers of a THICK plastic bag between the yoke and HV connector area to prevent arcing/corona...It works fine, and I did not hack up any OEM parts.
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  #25  
Old 11-11-2013, 08:25 PM
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Too bad, the 21AXP22 went to air. You paid less than I did for my Director, I think it was $125 and I had to drive to Indy to get it. Great scroe!
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  #26  
Old 11-11-2013, 08:34 PM
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So, I guess the CRT replacement options are pretty limited . . . .

Phil Nelson
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  #27  
Old 11-11-2013, 10:49 PM
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Phil,

We have the technology to locate the leak with the Helium leak detector. The leak will be located somewhere on the weld where the front and rear sections of the tube are welded together.

I believe Nick did some welding recently on some part of a 21axp22 that he is playing around with and commented that the material welded suprisingly easy.

So if we are able to locate the leak (which is easy) and Nick can re-weld the area where the leak is located, then it should be an easy task to re-gun the tube some day at ETF. I know somebody who has a stash of delta guns in the event we are able to get a rebuilding plant up and running at ETF some day.

Moral of the story is SAVE YOUR LEAKING 21AXP22 crt's. We might be able to fix them some day.

BTW: there is so much air in that tube that I can see corrosion on some of the gun elements.
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  #28  
Old 11-11-2013, 11:24 PM
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The AXP in my CTC-4 is gassy so I used a 21FBP22 as a substitute, and I can tell you it does work.
Any 21" good roundy color jug will work. With the glass jugs you need to remove the plastic CRT cover, make a new HV lead/plug, unscrew all the screen purity magnets so they are as far from the screen as they go, and ground the CRT's dag. On the non-21CYP22 tubes(I can't speak for the 21CPYP as I've never owned one) you will need to put some thick plastic between the metal yoke shell and HV connection on the side of the CRT to prevent arcing(because the grounded yoke will practically overlap the HV connector) According to a previous post I guess that some collectors prefer to cut a notch out of the yoke shell instead of using insulation to prevent arcing.

I'm not going to try to find my thread now, but to give you an idea of how good a deal you got...I shelled out over 400 clams for my CTC-4 pictured here http://s1095.photobucket.com/user/El...?sort=3&page=1 , and I have seen nice 4's on the bay go for north of a grand.
My restoration is on hold now as I moved and since then I have not been able to clear enough bench space to work on it....That and it has IF/AGC intermittents and alignment problems that I don't have the experience or equipment to properly address at present.

There was something else I was going to say, but I'm so groggy right now that I for got it as I was typing the last sentence...

EDIT: Bob's post jogged my memory. I was going to say the 21AXP22 CRT's are about as bad about going to air as the 15GP22....Only there is not as much of if any effort to create a successful rebuilding process.

PS: I'm saving my AXP and it's plastic insulator for the day when they can once more be rebuilt.
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Last edited by Electronic M; 11-11-2013 at 11:29 PM.
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  #29  
Old 11-12-2013, 12:08 AM
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Thanks, that sounds more encouraging. This set has a lot of potential. I really want to restore it to operating condition, not just keep it around as a doorstop.

Phil Nelson
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  #30  
Old 11-12-2013, 07:17 AM
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Thanks for the SN, Phil. Your set is now in the database.
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