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#1
05-02-2010, 01:37 AM
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Successful Rebuilt of a 15GP22 at ETF
Hi folks,
on the last ETF convention, a successful rebuilt of a 15GP22 by the French company RACS was demonstrated. Who attended the presentation, how was the rebuilt done, and which problems are still to solve? Some photos are kindly provided by old_tv_nut: http://www.flickr.com/photos/4200284...7623940164614/ Kind regards, Eckhard 
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#2
05-02-2010, 10:26 AM
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Hi Eckhard,
The main difference between the successful (so far) rebuild by RACS was the use of frit glass to seal the junction between the glass and metal at the front of the tube. The rest of the rebuild was normal. So far the tube doesn't leak, and displays a nice picture. We will watch it for the next few months to see if it continues to work. Here is a page with pictures of the original tube, the rebuilt tube, the frit glass seal, and the tube in operation: http://www.earlytelevision.org/2010_...tion_RACS.html Jerome Halphen is taking two of his 15Gs to RACS to be rebuilt. If they work, RACS will be ready to accept tubes for rebuilding. They have promised to provide a price for this soon.
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#3
05-02-2010, 11:36 AM
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That's VERY encouraging!!!! I hope however, that if indeed successful in the long term, we can get someone in the USA to do it. I'd hate to think of the nervous breakdown I'd suffer, mailing a 15GP22 to & from Europe. And I have the feeling that the FAA would have a problem with us buying an extra seat, and flying the tube by hand. I did that with a prewar Andrea TV (domestic flight in USA), but that was pre-9/11.
Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
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#4
05-02-2010, 01:10 PM
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I for one am optimistic that with the frit application from RACS, the puzzle might be solved.
Something occurred to me: On the 15G' the red phosphor is much less efficient than that of the green and blue. This was corrected by driving the red gun harder to make up for the lesser light output of the original red. Since the red gun is being driven harder, it serves to reason that it would wear faster. Since the gun is being redone as part of the rebuilding process, could the red gun be built heavier or with greater output relative to the other two, so that it lasts longer? Surely technology in electron gun construction has progressed over the last 60 odd years to allow for better lifespan and better emission. (ducking for cover)
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#5
05-02-2010, 01:37 PM
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Quote:
 http://www.semiconassociates.com/products/crt.aspx jr
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#6
08-08-2010, 12:47 PM
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Quote:
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#7
05-02-2010, 03:31 PM
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Steve, in the pictures there are some blemishes in the center of the screen, is that from debris that got into the tube or is it just dirt on the screen?
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#8
05-02-2010, 03:51 PM
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I know that you mean the other Steve but I can answer that. The three spots in the center are from contamination inside the tube. These spots were really not noticable when viewing something other than color bars. The rest of the spots are due to the fact that we forgot to clean the inside of the safety glass when we put the tube in!
Steve
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#9
05-02-2010, 03:59 PM
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I was standing around during setup. I recall some lamentation expressed about not having taken Windex to the safety glass ahead of time. There certainly aren't any dark spots on the phosphor plate.
EDIT: Steve, that is news to me. I didn't notice it at all and am surprised nobody commented on it. Last edited by David Roper; 05-02-2010 at 04:02 PM.
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#11
05-02-2010, 07:44 PM
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Quote:
John
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#12
05-02-2010, 08:05 PM
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I agree, since the point is one doesn't want to rebuild this tube more than once- due to the risk of stresses on the tube, and more importantly the cost. What's another $100 if it means greater longevity and a better result.
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#13
05-03-2010, 01:52 AM
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Hello,
you have to see the 15GP before rebuilding: http://www.earlytelevision.org/images/15G-before.jpg This is the worst candidate of all candidates for rebuilding. It is a CRT with a broken neck, and it is absolutely incredible that this tube came back to life and that the phosphors were not damaged by oxygen of the air. Absolutely incredible! Kind regards, Eckhard
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#15
05-03-2010, 11:40 PM
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Jerome,
I will be there Friday and looking for you to welcome you to our Delaware Valley Historic Radio Club monster meet at Kutztown. The place to be especially for you to take the congratulations on the 15GP22 effort. To those who missed the ETF convention and have seen the photos, it was every bit as wonderful as you can imagine. Pete and the two Steves did an amazing job cobbling this tube in a ETF donor cabinet with Pete's modified chassis. The first glow was a red flat-field from a generator albiet a bit blotchy. Then the fun began. Purity adjustments were odd. G1 adjustments were not responding properly. The distinct smell of ozone was in the air. That was a plate cap wiring fault and a spare was found but still continued to arc for the duration but did not affect the pix. The chassis socket connection had to be turned past it's 55 year historic natural position. That gave the clue that the guns may have been mounted out of phase. Moving the RGB G1 connections proved that. The original circuit design was specific for the colors and moving them around to get a picture did not involve moving all the circuits. Close counted in this case and it was good enough for the first try. Convergence was left for a later day. The colors were there and there was no giant sucking sound of air rushing in. And the set ran like Secretariat for the duration. The actual restored tube was something to see. The neck showed the usual glass welds and the original base was used even with it's missing chunks of base material and liberal amounts of adhesive showing. There were some splotches of contamination on the phosphor plate and given the train-wreck of a tube to use, it was not a deal-breaker. If you looked close at Judy Garland it could be seen but can be considered minor considering the success. And yes, clean the glass when you get yours rebuilt. The infamous glass frit solution was interesting to see. It looked like someone smeared epoxy over the seams and was only used in this case on the bell side of the tube seam. But it was hard as a rock. Jerome can inform further as to how this will be done for future tubes. There is still no known price for now. A work in progress that I was so happy to see happen right in front of me. Kudos to Jerome for his and RACS work on this and flying through volcanic ash to show us. Find him at Kutztown and congratulate his effort, Dave A
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“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes. Last edited by Dave A; 05-03-2010 at 11:44 PM.
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