Successful Rebuilt of a 15GP22 at ETF

[old_tv_nut]

Originally Posted by NewVista

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.

[JB5pro]

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.

[jhalphen]

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

[NewVista]

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

[jeyurkon]

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

[John Folsom]

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.

[Username1]

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.

[jhalphen]

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