View Full Version : CT-100 on eBay


Eric H
04-30-2011, 02:11 PM
Tube has enough vacuum to keep the heaters from burning up at least.

http://cgi.ebay.com/RCA-Victor-Model-CT-100-Color-Television-Receiver-/200603358204?pt=Vintage_Electronics_R2&hash=item2eb4e453fc

Phil Nelson
04-30-2011, 03:07 PM
Bogus refinishing job. The color's all wrong. The back of his cabinet looks more authentic than the front.

Phil Nelson
http://antiqueradio.org/index.html

jr_tech
04-30-2011, 03:28 PM
The one at ETF has a lighter finish as well, could that be a factory color? I agree that it looks strange with the darker color showing on the rear facing wood. :scratch2:
jr

Eric H
04-30-2011, 03:35 PM
The finish is wrong but since they usually need redone anyway it doesn't matter much. If the CRT is good it's worth the opening bid, that's a big IF.

Hopefully someone in the San Rafael area can do an inspection and report back to us.

Phil Nelson
04-30-2011, 04:58 PM
The one at ETF has a lighter finish as well, could that be a factory color?
Fading is common over time, especially with exposure to bright light. When I removed the CRT bezel on mine, you could see a big contrast with the original finish that had been covered since new. The original color was redder as well as darker.

Phil Nelson

Sandy G
04-30-2011, 06:10 PM
Pretty obvious the guy knows what he has....Wonder if its on anyone's database ?

videoguy
04-30-2011, 08:13 PM
But its been a long time since I did any electronics - used to work on tube hi-fi, guitar amps, and the occasional TV - 40 or more years ago.

Is there any easy way to tell if the CRT has vacuum - aside from the filaments lighting up?

Small tubes I remember had a silvery coating that would turn to white dust if the vacuum failed ,,,

leadlike
04-30-2011, 09:06 PM
The crt has a silvery getter as well, which turns white from exposure to air. You really need a crt tube tester to get any more info than that since the set is nonfunctional at this point.

Eric H
04-30-2011, 10:02 PM
A 15GP22 CRT can have a silver getter and still be gassy enough to not work.Here's an example from the ETF Site (http://www.earlytelevision.org/15GP22_rebuild_report.html)

I believe this was a rebuild that failed shortly after it was done.

http://www.earlytelevision.org/images/PURPLE-GLOW-1.jpg

ohohyodafarted
04-30-2011, 10:04 PM
Even if the tube is under partial vacuum, it could light the filiments have silver getters and still be gassy.. As sure way to test for vacuum integrity is to use a hand held high voltage tesla coil high frequency generator and apply it to the neck of the crt. If the neck gets a purple glow, the crt is gassy. If no purple glow it will have a good vacuum.

If it is not gassy and a crt checker shows good emission, then you have a useable crt.

miniman82
04-30-2011, 10:42 PM
Corona discharge in the HV cage and loss of HV would normally alarm me, but based on what I've seen here at the convention I'm no longer alarmed at CT-100's that do it.... 2 of the operating ones (one of which is a model 5) give off enough ozone to clean all the air in the building. lol

kx250rider
05-01-2011, 12:15 PM
The one at ETF has a lighter finish as well, could that be a factory color? I agree that it looks strange with the darker color showing on the rear facing wood. :scratch2:
jr

BADLY sun bleached. I had one that was blond on one side, and deep red elsewhere. That RCA red lacquer finish is very easily bleached.

Just to clarify; the only "factory issue" color was red. There were custom order sets in blond (I had the knobs and pencil box and insert from one), but those were special order only, and I only know of one besides the one my parts came from. CT-100MBO was the model tag. Same situation as the 1940s RCA 641-TS console combo. I had a 641-TS in bleached blond, which had special light brown bakelite knobs (as did the CT-100MBO). I got the 641 from the original owner, who ordered it and waited 6 months.

Charles

jr_tech
05-01-2011, 01:19 PM
Just to clarify; the only "factory issue" color was red. There were custom order sets in blond (I had the knobs and pencil box and insert from one), but those were special order only, and I only know of one besides the one my parts came from. CT-100MBO was the model tag.
Charles

So the custom order CT-100MBO would have been much lighter than the lighter set at ETF?

http://www.earlytelevision.org/rca_ct-100.html

Now it may be an optical illusion, but in the third picture on the ETF page, the "pencil box" looks more "gold" than red, and the grille cloth looks lighter, but perhaps these items have faded as well.

jr

radio63
05-01-2011, 03:47 PM
Yikes! That ballast resistor seems to be drooping at a very scary angle!

Gilbert

Phil Nelson
05-01-2011, 08:14 PM
The ventilated cover is held on the ballast base with a few little metal tabs. It's easy to bump it in that exposed position and leave it a bit crooked, even when the base is securely plugged in.

Phil Nelson

JB5pro
05-01-2011, 09:16 PM
have air inside and thus soon to total ruin...
Is such equipment accessible or within budget to: Place CRT in total vacuum chamber that one can then drill tiny hole in safe place to evacuate completely and apply proper sealant to new evacuate hole and glass to metal seam all while under controlled vacuum?
I have not read of this but it sounds doable to me.

vintagecollect
05-01-2011, 10:34 PM
It's interesting to see no one's bidding yet. Are the prices for these sets dropping? Wrong color, unknown status of electronics, weird "fire sale" of set all of a sudden that's been sitting around for years. The only thing these people know is that they want $2K and need it moved in less than a week. Sounds like a dream to me.:rolleyes::no::sigh:

Phil Nelson
05-01-2011, 11:46 PM
Many people use esnipe or similar software to place a bid in the last few seconds of an auction.

The cabinet color should not be a huge negative. Toning lacquer is cheap.

I only mentioned it so that people don't get the idea this is a common cabinet color (or good refinishing practice). If you're going to refinish a cabinet, why not make it look authentic? In the overhead view, looking down at the CRT, you can see the original color on the inside edge.

Phil Nelson

vintagecollect
05-02-2011, 12:14 AM
...

vintagecollect
05-02-2011, 12:17 AM
talked to a contact today about the ct100. They were honest when talking about the set.At some point, one tube was replaced w/ a diode. Turning on the set recently caused the diode to melt and liquify. A proper replacement tube was used and no HV present. The FBT has bad arcing out of the side of it now to the HV reg. tube. IS there anyone with ANY spare FBT for these sets? New or used.

kx250rider
05-02-2011, 11:00 AM
So the custom order CT-100MBO would have been much lighter than the lighter set at ETF?



Yes... It was "limed oak" color (basically painted yellowish off-white with tan grain filler in the mahogany wood). The knobs and pencil box were light beige in stead of the brownish reddish color on the familiar CT-100s.

Charles

TubeType
05-02-2011, 12:57 PM
For the record keepers, the chassis serial number is B1111566.

Kevin Kuehn
05-03-2011, 12:36 PM
It looks to me like it was striped of the original toner finish, and then clear coated over in its natural wood. Not original, but not too bad looking. Hopefully it's not a poly finish.

TubeType
05-04-2011, 11:42 AM
For the record keepers, the chassis serial number is B1111566.

Also, the cabinet and lid number is 472. The control panel insert number to follow.

miniman82
05-05-2011, 11:35 AM
Bump!

2.5 hours left, and no takers!

Tom Albrecht
05-05-2011, 11:47 AM
What is the slightly darker rectangular area on the front panel under the control door?

Phil Nelson
05-05-2011, 11:58 AM
It's a snap-out wooden panel, which conceals more controls. If you scroll down (and down, and down) in this article, you can see it in various pics.

http://antiqueradio.org/RCACT-100Television.htm

Phil Nelson

David Roper
05-05-2011, 12:06 PM
the cabinet and lid number is 472. The control panel insert number to follow.

Carnac says it's 472. :)

miniman82
05-05-2011, 02:02 PM
Went bidless.

I sent him an email, let's see if there is a response.

rcafan
05-05-2011, 02:12 PM
Probably nothing?? look at the ballast resistor just above the area
where the cover is tilted down,there is a black spot.
Possible short????

Electronic M
05-05-2011, 05:07 PM
If only I had a couple of thousand and lived on the east coast :drool:

If the ecconomy gets worse and prices drop who knows, maybe I'll be able to get or piece together a merrill on my shoe-string collecting budget.

Tom C.

Tom Albrecht
05-05-2011, 05:56 PM
East coast won't help you much on this one...

Electronic M
05-05-2011, 06:48 PM
OOPS! That is one of the worst typos I've made yet.

jeyurkon
05-05-2011, 10:00 PM
I heard through the grapevine that the seller accepted an offer for slightly less than the intial bid and that it will be picked up today.

I'll let the people who are more directly involved post the full details because after stories get passed along sometime things get muddy.

John

Tom Albrecht
05-05-2011, 10:20 PM
Well, one thing I can say is that it is not me. Thought I should clarify that since I am geographically close and was at least ever so slightly interested if the price had gone a lot lower.

miniman82
05-05-2011, 10:25 PM
If so, it wan't me. He didn't reply to any of my messages. Hope one of us gets it though!

ChrisW6ATV
05-06-2011, 03:26 AM
I am the guy who made a deal to buy the CT-100 after no one bid on it. I could not afford to spend the opening bid amount, so I made a deal for a lower amount that was acceptable to the seller, and I picked up the set tonight.

Details:
-The front panel insert is not #472, but is #733, 753, or 793. It has had some holes drilled in its inside surface to make room for the shafts of some replacement pots that were added, and one of them is through part of the stamped number. Two of the original dual-shaft pots have been replaced by a total of four new pots, visible in a picture that I will post later.

-Some work was done on the HV section. A solid-state replacement was installed for the 3A3 rectifier; it later went bad and a tube was put in again. Another tube was replaced by a solid-state diode as well, apparently; I will investigate further. I will post a picture later.

-The set has a temporary back panel that is from a Zenith Service-Saver TV. Again, a picture will follow.

Here is my first try at inserting a picture. Please let me know if the size is appropriate.

http://70.36.238.5/ct100/IMG_0355small.jpg

jeyurkon
05-06-2011, 07:17 AM
Congratulations on the acquisition!

I understand that someone tried to test the CRT. Any word on the results?

John

Sandy G
05-06-2011, 07:41 AM
I HOPE the CRT's good, but even if it ain't, just to HAVE a CT-100 is sumpin' pretty special, in my book...Congrats !

Electronic M
05-06-2011, 12:03 PM
This is purely conjecture on my part, but I think the restorer might have installed that SS HV diode as a easy way out of fixing a bad HV fillament winding on the fly.

Congrats!

Tom C.

jeyurkon
05-06-2011, 12:51 PM
If you could post the information about the cabinet refinishing that was done by one of the previous owners that would be great.

I'm really glad this went to someone local to it and didn't have to travel across the country again!

ChrisW6ATV
05-06-2011, 02:26 PM
Thank you all for the nice comments. The CRT test showed no emission in the test apparently, but I do not have enough details to know how exact or complete the procedure was. It was with clip leads onto a few of the CRT pins (as you would expect; I doubt there are any CRT testers with a socket for the 15GP22), and I do plan to do further testing. I have a B&K 467 CRT tester but I do not have the "universal adapter"-but this is an excuse to get the parts and make one!

I am waiting to get details of the cabinet refinishing. It is indeed a lighter color than the un-refinished areas on the edges, but it looks very nice overall.

Here are a few more pictures:

http://70.36.238.5/ct100/IMG_0347small.jpg

Inside of front panel insert.


http://70.36.238.5/ct100/IMG_0348small.jpg

Front controls, with extra potentiometers to replace original concentric ones (in right-side area).


http://70.36.238.5/ct100/IMG_0353small.jpg

Zenith(!) temporary back cover.

jeyurkon
05-07-2011, 12:15 PM
Hey, the cover keeps the cats out! Or other nosy critters.

Is that a Westinghouse electric range on the right?

Thank you all for the nice comments. The CRT test showed no emission in the test apparently, but I do not have enough details to know how exact or complete the procedure was. It was with clip leads onto a few of the CRT pins (as you would expect; I doubt there are any CRT testers with a socket for the 15GP22), and I do plan to do further testing. I have a B&K 467 CRT tester but I do not have the "universal adapter"-but this is an excuse to get the parts and make one!

I am waiting to get details of the cabinet refinishing. It is indeed a lighter color than the un-refinished areas on the edges, but it looks very nice overall.

Here are a few more pictures:

http://99.92.93.245/ct100/IMG_0347small.jpg

Inside of front panel insert.


http://99.92.93.245/ct100/IMG_0348small.jpg

Front controls, with extra potentiometers to replace original concentric ones (in right-side area).


http://99.92.93.245/ct100/IMG_0353small.jpg

Zenith(!) temporary back cover.

vintagecollect
05-08-2011, 06:50 PM
keep us posted please at least a several times on your progress for restoration. Pics always keeps it interesting. A few months ago someone else did awesome thread and showed great working pics off a jig to show their progress of producing a functional set. It was a 15" set from another maker. Detailed posts really keeps interests in these rare sets alive. Many of us wont have chance to own one, great when collector shares experience of finding such a set.

:yes:

ChrisW6ATV
05-08-2011, 10:43 PM
Hey, the cover keeps the cats out! Or other nosy critters.

Is that a Westinghouse electric range on the right?

The stove is a gas O'Keefe & Merritt model 9100-1. It came with the house when I bought it in 1989. Recently, I did a complete cleaning job on the stove and probably got it the cleanest it has been since it was new. Those old stoves, like many other items from the past, were really built well.

ChrisW6ATV
05-08-2011, 10:59 PM
More pictures:

http://70.36.238.5/ct100/IMG_0352small.jpg

The high-voltage cage. The empty tube socket in the left-center is for the 1X2B focus rectifier; there may be a solid-state diode underneath and not visible. I plan to restore this whole area back to the original circuitry to the extent I can.


http://70.36.238.5/ct100/IMG_0350small.jpg

The replacement volume/power knob. It looks pretty close to the originals I have seen.


http://70.36.238.5/ct100/IMG_0346small.jpg

The control box and knobs. The knobs are not the originals, but I may have correct ones in a box of knobs I bought years ago. (I know I have at least two, because I just saw them on a wood-cabinet 10" GE that I got without knobs and used ones from the box).

Eric H
05-09-2011, 12:22 AM
Wow, the HV might arc a little less if you just cleaned off all that soot!
Getting that Silicone off everything might be a challenge.

The Fly's on these don't put out all that much do they, most of it comes from a Tripler circuit doesn't it?

vintagecollect
05-10-2011, 01:33 AM
nice pics, interesting, had a early projector that had a HV tripler circuit. IS THIS the first commercially used trpler for a TV??

There's a patent link some guys invented in around late 60s for HV tripler ss box? IF
let us know of HV setup. this is the case, I'm surprised tripler design wasn't used more-- given all the flyback meltdown issues.

:yes:

Tom Albrecht
05-10-2011, 03:55 PM
Philco 48-2500 projection set has a tripler, and I think a number of other early B&W sets do.

jr_tech
05-10-2011, 05:10 PM
nice pics, interesting, had a early projector that had a HV tripler circuit. IS THIS the first commercially used trpler for a TV??

Tripler??? Am I missing something here... mine has a 3A3 HV rectifier. a 1X2B Focus rectifier and a 6AU4GT damper... I don't see a tripler circuit. :scratch2:
jr

Eric H
05-10-2011, 06:56 PM
Tripler??? Am I missing something here... mine has a 3A3 HV rectifier. a 1X2B Focus rectifier and a 6AU4GT damper... I don't see a tripler circuit. :scratch2:
jr

My mistake, I thought they used that setup.

miniman82
05-10-2011, 07:26 PM
21-CT-55 has a doubler, I think. A single 3A2 for focus, and another 2 for anode supply.

ChrisW6ATV
05-13-2011, 10:58 PM
I built a universal adapter for my B&K 467 CRT tester and hooked it up tonight. I have heater-to-red-cathode leakage, so I need to isolate the heater connections. All three heaters light up, and the blue, at least, does show some emission. I did not want to turn the heater voltage up to 6.3v until I get an isolation transformer on there, though.

Do any of you know if I could use an isolation-only booster for a B&W CRT for a test? I do have a couple of them here.

ChrisW6ATV
05-14-2011, 12:07 AM
I tried connecting a B&W brightener in "parallel-isolation" mode after verifying its output voltage seemed OK (connecting the brightener between the tester's heater pins and the CRT), but had no success. I will get a true source of isolated 6.3v for further tests.

ChrisW6ATV
05-14-2011, 01:41 AM
With a 6V, 2A power supply hooked up, the filaments lit up OK. The B&K showed low emission (but not zero) on red and green, and blue was in the low end of the Good scale. I tried the power supply on 7.5V (its next step) for a few seconds, and all three guns read higher (as you would expect), then back down to 6V. Now the blue gun is reading solidly in the Good range, almost half-scale, and staying there. I think it may be time to order some Vacseal!

Also on my list is to see if I could use my Sylvania CK3000 test jig with the CTC-2 chassis. I have already made the adapter for the CTC-4 and CTC-5, but this one is certainly different, with its electrostatic convergence at least.

ohohyodafarted
05-14-2011, 11:55 AM
Chris,

Sounds like your crt is asleep. IF it was my set, I would get the chassis up and running so I could power it under real world conditions, to see if the crt is any good. If it turns out that the tube is under vacuum and you do NOT have the dreaded purple glow, then I would use the Beltron to wake up and CLEAN the dirty cathodes to bring back the emission.

Or... if you have a hand held tesla coil, you could also see if the tube is gassy by applying the coil to the neck of the tube. No purple would indicate a tube under solid vacuum, and then I would proceed to the Beltron cleaning to wake it up.

ChrisW6ATV
05-14-2011, 02:34 PM
Bob-

Thank you for the notes. I do not have a Tesla coil, but I will proceed with the chassis restoration. (The set was apparently restored and working about 20 years ago, but I have not yet pulled it out to see the extent and type of work that was done, other than the HV picture above.) My CRT tester is a B&K 467, and it does have a clean/balance function as well as full-on rejuvenate (which would be a last resort, I am sure). I used the same model of tester many times in my work at airports to get good life out of tired tubes, but they were black-and-white CRTs.

I will post further as I make more progress.

jeyurkon
05-14-2011, 05:02 PM
If you didn't see a purple glow during the emissions test, then it's probably not gassy. If there was no emission then it could be gassy and not glow, but since you got good emission on the blue gun without it glowing then I think you're o.k.

John

kramden66
05-14-2011, 10:34 PM
before rejuving or cleaning with beltron or any other machine i would run it , after running for a while they may all come up and then there will be no need to rejuve or clean or whatever

mike

NewVista
05-15-2011, 10:06 AM
, but since you got good emission on the blue gun without it glowing then I think you're o.k.

John

Like Bob says, won't get true test of (purple) gas indication until all voltages present or a tesla coil is employed.

jeyurkon
05-15-2011, 10:42 AM
Like Bob says, won't get true test of (purple) gas indication until all voltages present or a tesla coil is employed.

The blue glow is from the gas being ionized. If you have emission you've got electrons moving and the couple of hundred volts used when testing a CRT accelerates them well above the few eV ionization potential of the gas.

If there were no emission, then yes the only true test would be the Tesla coil.

jeyurkon
05-15-2011, 11:10 AM
What's the purpose of the 2,700 ohm resistor in series with the Red cathode of the 15GP22?

Hope I'm not drifting too far off topic.

kx250rider
05-15-2011, 11:42 AM
If I'm not mistaken, that's because of the early type phosphor's inability to produce equal amounts of light among the 3 colors. The resistor compensates so as the chassis can put out an equal amount bias, while the TV watcher "sees" equal amounts of light.

Charles

miniman82
05-15-2011, 12:28 PM
Roundies have cathode resistors too, there are 3 on some so the guns produce equal amounts of saturation. Example: on sets which use the 21CYP22, the red is driven at full potential, where the others are reduced somewhat.

John Folsom
05-15-2011, 12:46 PM
Charles is correct.
From the RCA Color Television Home Study Course, Lesson Six

old_tv_nut
05-15-2011, 01:53 PM
Charles is correct.
From the RCA Color Television Home Study Course, Lesson Six

That's very interesting - I never noticed it before. Apparently besides the higher drive for red, they needed to make the current/voltage characteristic of the red gun more linear. Perhaps the much greater red drive made it more strongly non-linear than the green and blue, which would mean the midtones would not track the lowlights and highlights.

Username1
05-15-2011, 04:02 PM
Well thats essentially correct. The rgb bias settings are a low grey starting point, and the drive adjustments are for the greater beam current, or bright white adjustment. The drive adjustments are kinda like a linearity adjustment for the tube/phosphorus combo. as overall brightness is increased. I think starting with 2X beam current on the red gun for white, by adding a resistor in the cathode circuit would actually be a current limiter. So the question is would this be limiting the max current of the gun? Someone would have to measure what is going on at several current levels of each gun while maintaining white screen to see what this resistor is doing. Current limiting on a gun driven at 2X the current of the other guns for white....

old_tv_nut
05-15-2011, 04:19 PM
The theoretical relationship of gun current to drive voltage is a power law with a particular exponent, which has the same shape even if the three guns are driven more or less hard. The need for a series resistor indicates that the curve of light output is not exactly a power law, because the resistor will change the shape of the curve and make it more linear. This could be either an effect of the gun curve itself, or a non-linear effect of the phosphor. I think it is the gun, as phosphor effects usually consist of a loss of efficiency at high currents.
There is also some difference between grid drive (used for RGB in the CT-100) and cathode drive of the luminance (used in later sets), but apparently the later sets also found it useful to put a resistor in one or two of the cathodes even though they used cathode drive.

vintagecollect
05-15-2011, 07:11 PM
There's some old threads or discussions on how the new improved red phosphors were more red orange than true red. From what I heard the red phosphor was rare and hard to obtain? I really wish these weren't such finicky crts. Chris got a great deal, set had older restoration, picked up set locally and avoided costly shipping expense. That brass replacement knob IS actually solid machined brass and is quality. The finish is really a mood point, this tv is far from a basket case. Nice score.

:thmbsp:

old_tv_nut
05-15-2011, 09:11 PM
The standard NTSC red primary is a bit orangy - for example, traffic signal red is outside the gamut of NTSC.

The original red phosphors were close to NTSC standard. The all-sulphide tube (zinc cadmium-sulfide for red) was probably the most orange, and got worse at high beam currents. The vanadate rare-earth red was pretty close to standard. The europium red that eventually became the norm is a bit orangy again, but not as bad as the sulfide.
Vanadium and europium are "rare earth" elements.

ohohyodafarted
05-15-2011, 10:22 PM
RE: Beltron,

I just wanted to relate an experience I had with a 21cyp22. Upon testing it with a B&K 465 crt tester, the tube was devoid of all emission. I had very little hope of bringing the tube back to life.

I hooked up the Beltron and set the filiment voltage at 6.3 as normal. I waited for 10 minutes and only the green gun moved just a tad to about 10% of full scale. The red and blue showed no signs of life at all. I figured this tube was a gone'r.

I next moved on to the cleaning procedure. IN this mode the Beltron is used to "wake up" a sleepy tube. The procedure is to boost filiment voltage to 12 or 13 volts and let it cook for about 20 seconds. Once again no luck on any of the guns.

Well at this point there seemed to be very little hope that this tube could be saved So I proceeded to the restoration stage were the Beltron removes surface grunge from the cathode material to expose good material,( provided there is still good cathode material to expose.)

I raised the filiment voltage to 13v, and As normally happens the 2 large blue pilot lights flickered and blinked, I processed each gun as recommended for 3 cycles. As I processed each gun the emission got up to about 97% of full scale. I was very encouraged..

When I went back to test mode all 3 guns were now between 95% and 97% of full scale.

Now for the real test. I removed the Beltron and went back to the B&K 465 tester. I like this tester for a more accurate measurement because it has a nice large 4" meter and it seems to give a better quantitive measurement of the emission than the Beltron does. The scale is calibrated from 0 to 1000 where 200 is the cutoff for good and bad. If I get a reading of over 500 and 10 seconds life with this tester I know I have a very good tube.

I set the cutoff bias and proceeded to test each gun. I was ellated to find that each gun tested between 650 and 750 and had a life test of 16 seconds on the weakest gun. I have rarely ever tested a tube that went over 800 on the B&K, not even new tubes.

Absolutely incredible for a tube that was for all practical purposes totally dead on first testing.

It is my opinion that even if a tube can be awakened through boosting filiment voltage, or just opperating for an extended period, that in itself is not enough to bring the tube back to optimum performance, because you are still trying to boil off electrons from behind a dead layer of cathode material. Sort of like trying to piss through a window screen. The Beltron not only awakens the cathode, it actually has an ability to microscopically re-expose the cathode face so that it will once again emit a proper flow of electrons. A meer awakening of the cathode will not produce an equivalent result.

I have used the Belton on 50 or more tubes since I got the unit several years ago, and in some cases the crt is just plain dead due to lack of cathode material remaining. But if there is still viable cathode material available, the Beltron can exposed the material and bring back nearly full performance to a tube that was otherwise for all practical purposes, dead. And I have never damaged a tube with the Beltron. I can't say that about the B&K. I zapped the filiments on two 10BP4's with the 465 trying to rejuvenate them before I bought my Beltron. Now I only use the B&K for emission testing.

IF this 15GP22 still has a good vacuum, and the tube has weak emission, it is very likely that it can be brought back to very good performance with the Beltron. When you get the chassis up and running, see if someone in your area has a Beltron that could come over and test and possibly clean or restore your tube. You will need to build a 20 pin to 14 pin adapter to use the Beltron 14 pin socket. It can't hurt and it will possibly restore the tube to a very good performance level. At the very least it will improve it.

Good Luck and keep us posted on your progress.

Phil Nelson
05-16-2011, 02:45 PM
The original red phosphors were close to NTSC standard. The all-sulphide tube (zinc cadmium-sulfide for red) was probably the most orange, and got worse at high beam currents. The vanadate rare-earth red was pretty close to standard. The europium red that eventually became the norm is a bit orangy again, but not as bad as the sulfide.
Vanadium and europium are "rare earth" elements.
Is there a source that tells you what phosphors were used in various early color tubes? Just curious.

Phil Nelson

old_tv_nut
05-16-2011, 09:29 PM
There were a couple of papers on the subject, telling the sequence of development of each color of phosphor individually, but incomplete information on which ones were used together, and no specific information on years or tube numbers. The combos we do know are the original yellow-plus-filter for red, then the15GP22 phosphors, which correspond to the NTSC spec, then the all-sulfide tubes, and then the rare earth tubes, first with vanadate red and then europium oxysulfide red. But there are a string of reds listed between the 15GP22 and the all sulfide tube, and no hint of how long each of those were used, or if they were mainly lab developments.

old_tv_nut
05-16-2011, 09:39 PM
By the way, I have often wondered why RCA didn't try to do something to equalize the phosphor efficiencies in the 15GP22 (by reducing the green and blue efficiency with some sort of mixture of inactive material) in order to balance the gun currents better. There is probably some practical reason not to try it, but I don't know what that would be.

miniman82
05-16-2011, 10:53 PM
Me either, seems to me if you're gonna drive the red at max, why not drive them all at max? It's not like they stood anything to gain by not running the others at max, since any bad gun ruins the whole tube.

ChrisW6ATV
05-17-2011, 02:04 AM
RE: Beltron,

I just wanted to relate an experience I had with a 21cyp22. Upon testing it with a B&K 465 crt tester, the tube was devoid of all emission. I had very little hope of bringing the tube back to life...

IF this 15GP22 still has a good vacuum, and the tube has weak emission, it is very likely that it can be brought back to very good performance with the Beltron. When you get the chassis up and running, see if someone in your area has a Beltron that could come over and test and possibly clean or restore your tube. You will need to build a 20 pin to 14 pin adapter to use the Beltron 14 pin socket. It can't hurt and it will possibly restore the tube to a very good performance level. At the very least it will improve it.

Good Luck and keep us posted on your progress.
I appreciate the notes about the Beltron process. I have also heard that the newer B&Ks (467 which I have, and 470,480,490) and the Sencore CR70 are safe and (maybe) effective; the 467 has definitely worked well on the many B&W CRTs I have done. When I get that far, I will check around for anyone who has a Beltron here in the San Francisco area.

Username1
05-17-2011, 01:07 PM
"
By the way, I have often wondered why RCA didn't try to do something to equalize the phosphor efficiencies in the 15GP22 (by reducing the green and blue efficiency with some sort of mixture of inactive material) in order to balance the gun currents better. There is probably some practical reason not to try it, but I don't know what that would be. "


This is an easy one to answer, Think of how contaminants will act over time and possibly really degrade the tube's performance. Also as the tube ages why degrade a color performance new, and then possibly have that gun weaken, and need to be turned up, you limit yourself. I think back then fighting short tube life was a concern always.