Rejuvination of 15GP22's
 

Working on my CT-100 and have the horizontal, vertical and high voltage operating. The filaments on the 15GP22 light and the neck is not glowing but the raster is almost non existent. The brightness control does extinguish the light but it is really really dim. The room has to be pitch black. The getters are about 50% so the tube is/has been leaking. Anyone have cathode cleaner type rejuvinator??? Anyone had any luck bringing back a tube like this??

Just a thought. Have you tried turning the Red Screen control fully clockwise and then adjusting the Green and Blue Screens for white? Maybe it'll squeeze out a bit more light.

Pete

What does an emission test show, before you run off assuming it's got cathode issues? Could still be something with the chassis, for all we know.

Measure the DC bias on the CRT pins before you consider rejuvenation. Use a scope to check the video AC drive on the grids.

Hi John,
Worked for RCA/GE/Thomson designing color television chassis for over 20 years. I know it is the kine.
Jeff

I had a 1980s Philips/Magnavox that I noticed used an electronic power supply taken right out of a Motorola applications book! Did Thompson also allow such free reign/plagiarism in their U.S. designs?

I wouldn't try it until or unless it's 100% useless as-is. IMHO...

Charles

Jeff, I guess you do indeed know what you are doing! :-) My personal favorite rejuvenating machine is the Beltron, but I am sure others have their favorites as well. Best of lick with it.

I use a beltron and have great succeess with it. Some of the B&K's (my 467) seems to be a bit too rough on most tubes.
Real early tester/rejuvenators were brutal and did more harm than good. If it is a leaker, a rejuv won't help.

I had a 21FJP22 that had a crack in the neck, and was definitly leaking. The picture was a little dimmer, but was mostly blurry. I thought at first the HV was down.

Anyone have a Beltron I can borrow??? It is not at all usable so I haven't much
to loose. I live in central NH but will consider driving with the tube or pay shipping.
I think a few of the senior members can vouch for me.

I had a 1980s Philips/Magnavox that I noticed used an electronic power supply taken right out of a Motorola applications book! Did Thompson also allow such free reign/plagiarism in their U.S. designs?


I am sure IC suppliers do not mind if you copy their circuit. If you are using and buying their ICs. ALmost always the application or reference design isn't close enough to steal but can give you an idea on how it works. I usually used more generic ICs and discrete transistors.

Hi All;
JBL, What era of Color TV's did You Design ?? Tube, Transistor, IC's, Etc.. And What Part of the Set did You Design ??
THANK YOU Marty

Maybe it's time to have one of your own? They've been going very cheap on eBay lately.

http://www.ebay.com/itm/Beltron-Mode...-/290911612494

I like the B&K 467 / 470. It doesn't whack the heck out of the cathode; the way the 465 did, but honestly I've never had a Beltron, and don't know what method it uses. The 467 heats the tube, then gently does a burn-off of the cathode as the filaments cool. No loud pops, and in stead of a big yellow flash, there's a corona-like arc that you can see, as the oxidation falls away from the cathode coating.

Charles

I started in 1982 working on getting the CTC-120 and CTC-131 in production. Convergence for CTC-132. Designed deflection and power supply circuits for CTC-148/149. Power supply, analog stereo and YPRPB version of the CTC-169. Video circuitry CTC-172 1st HD 16x9, All Video for the MM-101 monitor, All Video for the DTV-306, Video decoder and interface module to use the DTV-306 with a DLP light engine we purchased. Digital Video, color wheel, etc for RCAs own DLP light engines. And a few chassis along the way that never saw the light of day. Left in 2006 and during the Chinese take over of Thomson's TV business.

I also was a big TV collector. I've since focused on Victor phonographs, acoustic and the first electronic. I guess my day job soured me on TV collecting and most of my TV's were traded away. I must have owned over 20Started collecting them when I was in college. Collected radios, TVs and phonographs since before I could drive.

I remember this model from the TV repair shop I worked at during my college days! I will have to bid on this one and watch the B&Ks.

I doubt I will use it more than once though.

Well considering the options available I think you should try a radical approach.

If I had a 15G in the condition you have, I would try this:

Build a box the tube can fit in comfortably, make it capable of sealing, vacuum tight, and make it heat resistant to 300 degrees f. Metal box??? Glass???

Put ac air conditioner fitting on it, and get a cheap deep cycle vacuum pump. and good digital gauge. $400. you could resell later.

Seal it up and apply vacuum and be sure it holds vacuum for a few days with no leaks.

Then for a period of one year keep a full deep vacuum 200 microns of less, and keep it heated at least 200 degrees to get out any water vapors.

After one year of this treatment remove the tube and test it, if there is significant improvement then seal it with that vacseal at all known leak points.

If no improvement oh-well it was dead anyway.

From the Department of Nutty Ideas, Podunk, MD division...knowing almost nothing about such matters...can a crt be rigged to run with a vacuum pump in place and running? I recall reading about a projection system that worked this way.

Hi All;
I am intrigued by Squirrels Idea, But, I can't Imagine what my Electric Bill would look like each month, from running the Heat Oven, even as low as 200 degrees.. I have a 10BP4 that possibly could use that treatment, but it might be a low emission Cathode.. I think my other 10BP4 though is just dead.. Not to say anything about what and where would I get the Vacuum pump assembly..
THANK YOU Marty

What an interesting idea.

...

For what it's worth We used to lay the crt facedown so when you hit the rejuv button any of the crud that flew off the gun assembly would fall down toward the screen instead of flying around the gun assembly and causing problems later.

for what its worth II, If a vacuum is generated in a system not leaking and holds, then the pump is only running a short time each week, to deep vacuum what is coming from the tube. Heat need not be constant, but possibly only a few hours at a time since you would be aiding what the vacuum pump is doing. Lets say you sat it out in the sun each day and did it only in the summer, so 6 months not a full year. Or built a solar hot box, build more heat than just sitting in a sunny spot. My solar panels easily put out over 115 in the summer when they are much less efficient. You would only need to supply a small amount of additional heat, possibly a 100w light bulb or two's worth.

I reclaimed an open to the atmosphere 3 ton A/C unit and vacuumed it down to where my gauge didn't even begin to register daily for a few days during the hot summer days so the heat of the day would aid in removing the moisture from inside the unit. After a week I had it down to less than 200 microns and held since.

Seems to reason, with a leaking tube but still getting some emissions, you may have something that can be reversed, and recovered, if the idea were given a test.

Since the 15G Has a unique problem of slow leaking, then restoration of vacuum would need to be done slowly over time. If it works, then you also have a few hours to coat it with a known sealer.

200 degrees is achievable and much safer than much higher temps.

I would imagine since the tube has not just been rebuilt, then removal of some materials that would vaporize at higher temps would not be necessary, it would just need removal of standard atmospheric elements. Like water vapor.

Imagine if it could be done and worked...... A few 15g's out there in this condition..... No face cracking chance..... complete implosion........

The worst thing you might need to do then, which I would try instead of a rejuvenation attempt, especially since it involves raising the heater voltage, which by the way heaters exposed to higher voltage in a less than perfect vacuum will surely fry, the thing to try would be reactivating the getters with one of those rf getter coils and see if you can use that to take care of anything left in the tube that needs gettin'

Fun stuff to think about...BUT the usual mechanical pump used to pump out AC systems before recharge is orders of magnitude poorer than the vacuum needed inside a properly processed CRT. About 10 to the -6 torr is necessary, and that's before getter flash!

jr

yup, you are right..... But an A/C pump is only $200. and can be resold. A Diffusion pump is tons more and not easily resold. Besides when I was a kid I made light bulbs with a small wire, a jar, a piece of plastic, and a candle to burn out the air inside the setup, sealed with wet wax. So I would imagine a A/C vacuum pump can come closer to a good usable vacuum level than a candle, again worth the experiment.

And if the tv museum got the crt rebuilding stuff, then they got a diffusion pump, and a getter coil.... It can all be done there with that stuff......

The diffusion pump would almost guarantee a good tube if this were to work. I guess that pump could be used on the last day of vacuuming out the enclosure.....

What kind of equipment do you think they had to make the first light bulb, or tube.... Not the best since they were pioneers.

I bet with a leaking bad tube, a way can be found, or should be tried to fix it without cracking it open. Should be worth the experiment.

The result will surely not be perfect, but will not crack the tube, or contaminate the inside of the tube.

let me tell you you did a fantastic job there. i sold tons of those sets. my favorite the great ctc169 fixed a zillion of those always simple repairs.

I like the CTC-121 with the flip-up metal door atop and stereo speakers and on-screen-display.Those sets had a huge remote control and composite video inputs too. A neighbor has one and I always ask for it :)

.......
 

..In the interest of not getting side-tracked here, I will comment on the early color tubes.
I'll tell ya, I'd be more interested in finding some of the RCA studio gear from that time--the "mil-spec" color tube-chassis monitors to do air-checks, and stuff like that. Where are all of those monitors from the '50s? One can only imagine..
I applaud the extensive efforts being made to restore 1950s color TVs.. I cannot say i have ever worked on one.(or ever seen any)

The technical knowledge/prowess displayed here NEVER ceases to AMAZE me...

Also, let's not forget it was just about the only set besides the CT-100 to have full I/Q color demodulation. I have one and the picture difference is very noticeable, especially with pastel colors.

I have one: an RCA TM-10 using a 15GP22. Restoration is underway, but this is not a trivial project (for me, anyway), so it's taking a while.

http://antiqueradio.org/RCA_TM-10_15GP22_Monitor.htm

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

One less Rube Goldberg-esq method I've heard of that was supposedly successful in fixing a gassy 15GP22 was to run the filament continuously for over a year to boil the crud off the cathode and cause the gas to move more so as to get it to hit the getters and be absorbed....I'm tempted to try it on my gassy 21AXP22.

I worked on the CTC-131 and it was the first to have full wide I. The CTC-121 appeared a year earlier but was not wide I. The CTC-131 also has an auto kine bias set up. Which does track low lights over time.

I tried this and was able to achieve a raster but it still had the fatal Purple Glow :sigh:

That's a nice General Electric tricolor receiver! Back around 1970 I had one of these in the goodwill repair shop in as a DONATION! We got it working very well and sent it out to be resold for $100.00. The 15gp22 was still under vacuum! It was the first and last one of that receiver I ever saw come through the door. Someone actually bought it.
I wish I knew then what I know now- I'd have paid the $100.00 to rescue it.

But then who wouldn't.

Pallophotophone

Correct me if I am wrong, but I think it is normal for the getter flash in a vacuum tube to be used up over time, not specifically indicating a loss of vacuum.

The only thing that "uses up" a getter is adsorbing gas. But a depleted getter doesn't necessarily mean a leaky tube. Gases can also be released internally, usually as a result of overheating or arcing, but sometimes as a result of insufficient degassing of the mount during evacuation.

You often see faded/discolored getter spots on power tubes (like horizontal output tubes) that have seen many hours of hard service.

Absolutely. 7591, 6L6GB, 6550, you will often see the getter flash that looks kinda like a cola color. But I have had many that still worked just fine albeit a little weaker than NOS but still worked fine...

Doesn't the CTC-133 also have full I bandwidth?