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

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.

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

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)

Dispenser Cathode, perhaps? :scratch2:

http://www.semiconassociates.com/products/crt.aspx

jr

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?

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

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.

I think you'll find that Semicon's dispenser cathodes would cost way over $100 each in small quantities.

Considering the cost of just shipping a CRT to RACS, that might not be so unreasonable.

John

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.

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

Good day Gentlemen,

Some of my pictures of the 15G's original condition as it was entrusted to my care exactly one year ago.

Best Regards

jhalphen

Philadelphia, PA

Hi again,

ETF 2010 Pictures, my shots.

Best Regards

jhalphen
Philadelphia, PA

PS: Any TV collectors at the Kutztown/PA Radio Meet this upcoming weekend?
I will be there & wear my ETF "dog tag".

Just amazing!

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

Hi Dave,

What can i say! (blush):)

Will be glad to see you & other ETF collectors at Kutztown.

Latest news with RACS is that i will send my two 15G's for rebuild simultaneously. They are not too sure about the feasability of the CRT with the entire front bowl detached so i will also send my operational tube which has a Red Gun 99% dead.

Best Regards

jhalphen

Where did the gun assemblies come from for this rebuild?

Bumping this up to the top. It's been about 3 months since this rebuilt tube was demonstrated, I was curious to know if the tube has remained sealed? I seem to recall John and Bob's rebuild attempt at Hawkeye sadly went to air again within a month or 2 of their rebuild.

I believe most want to know if this rebuild is still under vacuum.
Has the rebuild been installed into a working set? Is it used? That is, is it powered up and watched regularly? Has the tube been allowed to reach operating temperature and then powered off/turned back on? Has the tube spent its rebuilt life in a shipping container stored in an essentially constant temperature environment?

The RACS rebuilt 15G lives in a restored CT-100. The Early Television Foundation posted an update saying that it was still working fine on June 6th.

No news is good news...?

Still working today. I'll update the site.

The tube is in a working CT-100. It survived an air shipment from France, and since then the room it is in has ranged from about 70 to 85 degrees. We turn on the air conditioning on the weekends, then off during the week.

Jerome Halphen has two more tubes that he plans to take to RACS soon.

I assume the issues sourcing electron guns remains?

At the present time, and for the near future at least, there is a place to have the existing guns rebuilt.

Humidity ?
 

Humditity ?

Humidity also changes. When the air conditioner is on (weekends), humidity is relatively low. During the week, it gets up there - Ohio summers are typically very humid.

The impression I get from this site is we have not only some of the most intelligent and knowledgeable people in the world but also some of the most successful in general and therefore it is likely somebody could get a private jet to transpost a 15G. Just a guess but I seem to more often be right that wrong... too many words again? Maybe still too crazy/pscho sounding? :)

In case I missed it, how do you tell if a tube like 15GP22 / 21AXP22 has air ? As you would want to know and be cautious testing. Do they all have neck getter to look for for instance ?

There is much detailed info about this in at least one thread but if the getter is dark rather than silver it prolly has enought air to burn out filaments. If the silver is good but has that classic "gassy" look to the picture than it is gettin aired up and likely soon to burn out filaments. My info may be off a bit in one way or another.

The inside black conductive coating on 21AXP's have what looks like a "window" strip at top of guns .25" x 1.5" (dark silver non transparent) - is this the getter ?

Where is getter on 15G's and what size is it ?

I look on later 21" color roundies and they only have conductive coating + 1" red band - and no getter ? (because they were more confident of seal ?)

All tubes must have a getter. It is essential to getting the final vacuum quality, even if the tube does not leak. Sometimes it is somewhere not visible, like under the conductive aquadag coating.

I think it is an incedible and beautiful thing that all of you great men are doing to restore these 15G's. I just had to write that.
It will be amazing to me to someday see a picture on one in person.

Good day Gentlemen,

I have been procrastinating over the summer (RACS closed) to decide weither to send my working 15GP22 for rebuild straight away, or attempt a last resort test to revive the nearly dead Red gun.

I have also received 2 sturdy CRT boxes to ship the 15Gs.

As of now, Blue & Green guns are A-OK, the Red gun needs a "preheat" for 30-40min at 7V to display red. If the set rests for a week, the process must be done again.

RACS suggested i do the following test to decide if the Red gun is revivable before deciding to ship it to them:

TV off, socket removed, power to filament only:
- 7Volts, 1min
- 9V, 1 min
- 10V, 1 min
- 12V, 2min

Reduce to 9V, "cook" for 45min.

Then, Connect K(Red) to G1(Red)
- Connect a 40W/220VAC light bulb between K+G1(Red) and G2 (Red)
- Apply a 300VDC source between K+G1(Red) and G2 (Red)
- Duration 30 to 45 min.

Question 1: i have a solid-state DC/DC converter, 9V to 300V, 30mA, do you think this intensity is enough?

Option 2: Eckhard is kindly offering help under the form of a Müter BMR90 or Müter BMR 107 CRT rejuvenator.

Quote from Eckhard:
"I have brought an absolutely weak red gun (zero beam current) back to life with 0.9 mA after rejuvenating and with a lifetime guarantee of 2,000 hours (according to the manual). The rejuvenator has a computer-function which measured the actual emission of the gun and computes the exact rejuvenating power for the best results". - sounds encouraging!

If i go for this option, i will need to build a socket adapter for the 15G. From the GE pdf on the 15G it uses a JETEC-20A type base (see refresher data below).

Would somebody have a NOS, second hand, retrievable connector from a dead PMT tube or a source that still sells these? i looked at Digikey's bewildering choice of connectors, got lost & found nothing. If you have something, please PM me with price + Airmail to France.

Hammamatsu Photonics sells new ones for use with nuclear research PMTs. Before contacting them ( high $ price and probably won't sell alone without a PMT tube order) i am trying my luck here with the ressourceful VK gang.

Once this is sorted out, 1 or 2 of my 15Gs will be sent to RACS for rebuild.

Thanks! for reading this long message,

Best Regards

jhalphen
Paris/France

You can make an alligator fan-out adapter to test unusual tubes :tresbon:

The DC/DC converter should be able to handle the load. Just to be clear, the light bulb should be in series with it. The instructions you listed makes it sound like it's in parallel.

I can send you a socket if you would like one. Send me a PM.

John

Jerome, if it will help, I can loan you a 15G to 21" adapter, which you can return when you are finished. It is a spare, so no hurry on the return. Just let me know and I will get it in the post.

If it were me I would do the heater cooking
TV off, socket removed, power to filament only:
- 7Volts, 1min
- 9V, 1 min
- 10V, 1 min
- 12V, 2min
And then use the super-duper crt rej. machine. Mostly because the other steps in the home fix include biasing the tube on full and then letting it sit for a long time at an unknown current flow through the cathode. This could easily burn off too much of the remaining cathode stuff. If anything on the home grown front, you can cook the heaters, turn on the set with the elevated heaters, and whack the neck of the tube while keeping the higher heater voltage and using high brightness setting. That way you keep the beam current to within the specs that the tube will have to run at when being used normally..........

While you may not think whacking the neck of the tube is a good idea, keep in mind the rebuilding process can kill the tube entirely, as in crack, implosion. Whacking the tube with a screwdriver or some other hard item to shake off some of the carbon buildup ; ) on the cathode is really what the crt rebuilder does. In both the whacking method, and the rejuvinator method, you will see a little spark jump inside the tube, when you achieve this you are done. The rejuvinator most likely does the little spark thing the right way, so you should use the fancy computerized rejuvinator thingie.

Hello Squirrel Boy (cute Avatar!)

Thanks for your advice.

I am awaiting delivery of the 2x CRT testers kindly loaned by German friend Eckhard (see pictures).

The CPU auto-regen programme of the Müter 107 does not advise filament pre-heating as this can mess up the CPU-Controlled regen sequence (true emision).

Manual filament increase voltages: i've tried it in the past months, it works for demos but after several day's rest (7-10 days) the zero Red emission condition comes back, so this is not a time-durable solution.

RACS rebuilt with success a 15GP22 CRT, totally destroyed for years (spiders in the neck) with a broken/separated gun/neck assembly which was displayed at the ETF Convention 2010 working A-OK with flying colors. 6 months later, the CRT is still A-OK (no leaks) and producing great pictures.

If i send mine to them, they are my best chance to rebuild with success a nearly 60 year old color CRT.

Best Regards

jhalphen
Paris/France