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  #76  
Old 10-23-2014, 03:00 PM
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You have a DuMont RA-101-1A:

http://www.myvintagetv.com/dumont_101a.htm

A better forum to find out stuff about old TVs is:

http://www.videokarma.org/forumdisplay.php?f=19
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  #77  
Old 10-25-2014, 02:23 PM
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Steve-

I am happy to read about all the progress that you and others have made with the CRT project. One thought I had, now that I have read both the entire Web page as well as the discussion here: I noted that the heating element is from a convection oven. Would it be feasible to obtain and use the element(s) from a self-cleaning electric oven? During the self-cleaning process, those ovens go up to maybe 800 degrees, if I remember right. Such an element would need 220V wiring.
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  #78  
Old 10-25-2014, 05:16 PM
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Quote:
Originally Posted by ChrisW6ATV View Post
Steve-

I am happy to read about all the progress that you and others have made with the CRT project. One thought I had, now that I have read both the entire Web page as well as the discussion here: I noted that the heating element is from a convection oven. Would it be feasible to obtain and use the element(s) from a self-cleaning electric oven? During the self-cleaning process, those ovens go up to maybe 800 degrees, if I remember right. Such an element would need 220V wiring.
He is right. We have an electric self cleaning oven. It is 220v and the instructions
do say not to touch or open it, temperatures will reach 750 - 800 degrees....
I have never used the self cleaning option....

.
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  #79  
Old 10-26-2014, 05:19 AM
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There is nothing unique about the heating element in self cleaning ovens. The one I'm using with the fan is from such an oven. Mine is 8400 watts at 240v.

The reason I am having more difficulty reaching 700 degrees relates to the size of the oven (4 times the volume of a typical oven) and air leakage.

I am in the process of using an automotive silicon sealer on all the interior joints of the oven. If this doesn't bring it up to the desired temperature I will add an additional heating element - like a stovetop element. I can add about 1400 watts and still power it from my 40 amp breaker.
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  #80  
Old 10-26-2014, 01:11 PM
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One thought on 7JP4 rebuilding. There were many essentially identical scope tubes made so if a gun gets shattered in transport or something similar, robbing the parts from a less sought after scope tube may be a solution. It could also potentially be worth wile to rephosphor otherwise identical scope tube types to make new 7JP4s.
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  #81  
Old 10-26-2014, 01:24 PM
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Unfortunately, just robbing the gun from a 7JP1 scope tube won't work.

Once the tube is let down to air, the cathode needs to be replaced, because the active oxides become contaminated. If you are going to go through all that trouble, you might as well just rebuild the 7JP4 guns themselves...
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  #82  
Old 10-26-2014, 09:02 PM
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There is nothing unique about the heating element in self cleaning ovens. The one I'm using with the fan is from such an oven. Mine is 8400 watts at 240v.
OK, that is good to hear. I hope things go well with the insulation and sealing efforts.
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  #83  
Old 10-27-2014, 03:33 PM
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Quote:
Originally Posted by N2IXK View Post
Unfortunately, just robbing the gun from a 7JP1 scope tube won't work.

Once the tube is let down to air, the cathode needs to be replaced, because the active oxides become contaminated. If you are going to go through all that trouble, you might as well just rebuild the 7JP4 guns themselves...
I was NOT trying to say that if the cathode is dead in a 7JP4 to just swap the gun from a 7JP1. I understand that the cathode would need to be rebuilt. Someone earlier insinuated that the guns on 7JP4s were very fragile and may be damaged in shipping despite the rest of the CRT being fine, and I was responding to that by saying that if the gun is damaged beyond rebuild-ability one that could be rebuilt and installed might be obtained from a scope CRT....That and one could potentially make new 7JP4s by rebuilding a 7JP1 and rephosphoring it with P4 phosphor.
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  #84  
Old 10-27-2014, 08:19 PM
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I'm hoping someday they can make a bunch of 3KP4s out of all the 3KP1s I've been saving.

.
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  #85  
Old 10-27-2014, 09:51 PM
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Originally Posted by WISCOJIM View Post
I'm hoping someday they can make a bunch of 3KP4s out of all the 3KP1s I've been saving.

.
That has the potential of being even more lucrative than doing the same with the 7" CRTs. There would be a lot of happy Pilot TV owners...
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  #86  
Old 10-29-2014, 10:26 AM
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Here is a video produced by Bob Galanter that shows the rebuilding process used at Hawkeye:

http://antiquetvguy.com/Web%20Pages/...ie%20Page.html
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  #87  
Old 11-14-2014, 01:48 PM
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The oven is now working perfectly. Take a look at our latest progress report:

http://www.earlytelevision.org/crt_project.html
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  #88  
Old 11-21-2014, 07:02 AM
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The RACS equipment is halfway across the Atlantic. It should be in Norfolk on the 26th, then in Hilliard by about December 1.
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  #89  
Old 11-21-2014, 02:45 PM
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Thanks for the update!
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  #90  
Old 11-22-2014, 08:10 AM
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The RACS equipment is halfway across the Atlantic. It should be in Norfolk on the 26th, then in Hilliard by about December 1.
It's an early Christmas miracle .
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