Rca ctc-5h
 

A few weeks ago my son and I picked up this set in the Chicago area. Today I finally repaired a simple emission type CRT checker I've had sitting around since last year. I hooked up the checker to test the guns of the 21AXP22a CRT. It took about 2 to 3 minutes of waiting to get these readings on the scale. I also noticed there is a purple glow toward the forward CRT elements. Is this condition normal for this type of CRT that's been idle for years?
If the CRT is usable still, then I will proceed with a recap. The power transformer checks OK. Haven't checked the flyback yet. I still have two other B&W sets to recap and test.
ED

It the CRT passes the short and gas test I would take a chance and recap the electrolytics.
Phil

Have you tried your tester on any other CRTs? That might tell you how much weight to give the tester's opinion, especially if you test some known-good CRTs as well as a dud or two. Testers vary in quality/sophistication, like other devices.

In my experience, CRT testers don't always tell you the whole story. I have seen CRTs that look weak on a tester, but make a fine picture when used in a TV. The best tester of all is a television.

Also, if a CRT hasn't been used in a long time, it's common for it to "wake up" and show stronger emission after it has cooked for a while on a tester at normal or slightly elevated filament voltage.

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

I tried the tester on some good and not so good B&W crts. The results reflected what I knew from in set testing. I agree Phil, in set testing is the best indicator.

The crt shows no shorts, but the gas test seems quick to decline and slow to rebound? Looks like I have good reason to proceed.
Thanks Phil and Phil.:yes:
ED

Purple glow between elements of an electron gun is not a good sign. The voltages a crt tester produces are rather low compared to what the crt will be using when it is in operation.

Typically, if you see inter-element purple glo, and you use a Tesla coil to test if the tube is gassy, you will find that the entire gun area in the neck will light up with a gassy pink/purple glo.

I purchased a 15GP22 about a year ago. On my Beltron tester, I was getting very high emission readings, but there was faint inter-element glow in the gun elements. The With a B&K 465 crt tester the glow is much fainter. When I applied the high voltage from my Tesla coil, the entire neck area lit up bright pink/purple showing that the tube was gassy. You can also see a blue-violet glow between the G1 and G2 gun elements

There are 2 ways to be sure if the tube is gassy, Tesla coil or an operational chassis. I have found anything else will not be a definitive test for gas.

Three photos of gassy 15GP22. Beltron emission readings, Inter-element glow on the Beltron crt tester, and Lots of glow with the Tesla coil.

Posting good photos of the kind of glow your 21AX produces would be more helpful.

All that said, there is still a possibility your tube may be OK.

I learned in the process of testing my now confirmed good 15GP22 in my Westy that, without a working chassis, the best test of a CRT's suitability is a Tesla coil and a Sencore CR-70. If cutoff responds normally, and the Tesla coil fails to produce any substantial glow, then you likely have a winner. Given your description, I think you have a dud though.

I'd be interested to see what people are using in the tesla coil arena.

If you know your tester and it's gas test well the more heinous gassy CRTs will have a distinctive fail characteristic....
One nutty thing you could try is to take a monochrome chassis with 20KV or more of HV and connect the CRT leads from the chassis to one gun (with clip leads), then connect the HV. With the brightness at minimum it should produce a center dot on the screen, but if the tube is gassy there will be an arc inside the tube between the HV and the electron gun.

Likely something like this... widely used in science labs, by tube builders, and perhaps stock yards for decades.

https://www.amazon.com/Oudin-Coil-Te...rds=tesla+coil

https://www.amazon.com/Electro-Techn...J0RRDTNFN23F1B


not affiliated
jr

After seeing your center picture Bob, I tend to think the crt has seen better days. Ben I don't have tesla coil tester but I bet your correct about it being a dud.
I find it difficult to get a good picture of the purple glow in the crt gun. I'm still going to recap the chassis and try the crt just for the experience. The last photo is with my camera set for nightime exposure, for more light.
Ed

We had one of those as standard equipment, called it the Cattle Prod.:lmao: Used it for 'cleaning' rebuilt CRTs before installing them.

Rebuilts tended to arc due to contaminant particles. The Cattle Prod made the particles incandesce and fly around until they stuck somewhere, thus minimizing arcing after installation.

Word to the wise only recap the power supply and sweep circuits. The rest should be able to last past a check of the CRT with HV applied.

Thank You gents for explaining and showing pictures of the tesla coil . I have one in my collection that came from the contents of the Radio/TV repair shop I was lucky enough to get , and wasn't quite sure what it's use would be in TV repair work .

You can find "tesla coils" listed as Master High Frequency on ebay. Used in the field of cosmetology and skin care. Make sure you buy a "working" unit. These units heat up and burn out when used for prolonged periods of more than 5 minutes. Dumb cosmetologists often over work these units and burn them out.

You will need to make your own metal pointed probe if you buy one of these with the glass skin care probes. But it is cheaper than paying $250 for a new one.

https://www.ebay.com/itm/Vintage-Mas...4AAOSwGJlZL6Bu

And I had been trying to sell one of these at radio meets for $55 as a quack device. Now that I know they have a good use, I'll be holding on to mine! (Thanks, Bob!)

.

Good to know those work for that purpose...Now I know what to look for.

Today I reached the point of testing the 21AXP22 crt with the recapped CTC 5 chassis. As many of you suspected, the crt is a useless gassy dud. It produced pretty swirling colors of pink and purple along with a few sparks in the neck.
I have a 21FJP22-a from an old Zenith set. I was going to try this crt with the ctc5 . That way I could test out the deflection and high voltage circuits.
Has any one used a newer crt in a ctc5? If you did, did you reuse the original plastic crt cover and yoke assembly? Can I remove the 21FJP22's current banding and mounts to fit the crt into the ctc5's mask?
Ed

Ed, I have a CTC-5 Deluxe chassis model. It has a 21FBP22A/21GUP22 replacement tube. Fortunately it has an RCA metal to glass tube mounting conversion kit. This allows the installation of the new tube to the existing mounting receptacles w/o using the 21AX plastic shield. The original yoke was retained.These kits are extremely hard to find and other various homemade mounting hardware has been used for installing later model 21" round tubes.

-Steve D.

Given the existing mounts on your replacement tube ED it looks like you should be able to loosen the band, slide the brackets to the right position to bolt to the cabinet, tighten the band and be good...Don't know if the degauss shield can be kept, but it may not be needed in the mounting anyway.

Back in 2004, I used part of the mounting hardware from a CTC-7, along with some make-shift brackets, to mount a glass tube in my CTC-5. Unfortunately, all of the pics in that thread have disappeared. Of course, I saved all the CTC-5 hardware and used it later when I got a 21AX for the set.

What i did on one of mine was remove the mask to get at the original mounting bolts and replaced them with longer ones. I then reused the plastic housing which slid back in place as it is only slid out about an inch and a half from the original crt position hence the longer bolts. Of course i had to take a hole saw to the side of the housing so i could hook up the anode lead. The outer magnets and hardware were removed from the mask. The good thing about this route is everything can be put back original if a good 21axp22 is found or if the old one can be rebuilt. The chassis had to be slid back an inch because two tubes were right up against the housing but this might not be an issue depending on what cabinet you have.

Thanks for all the replies,
Thanks for posting those pictures Steve D.
I like the approach you took Tony V.
Tom, I not sure the Zenith brackets will work with the lack of space, but I'll check.
Old TV Nut I read your old thread from a few years ago, when you put a 21axp22 back into your ctc5 :thmbsp:.
From reading everyone's suggestions, it looks like the purity magnet assembly should be removed that surrounded the old, first.
Thanks for all the help,
Ed

Right - the edge magnets were totally unnecessary with the glass tube, and actually may be mechanically in the way and magnetically may make things worse.

I ended up trying Tony 's approach to mounting a 21FJP22a crt in the CTC5.
Four longer bolts and cutting a hole for the HV lead.
I encountered two issues and was wondering if Tony had the same issues? One is that the deflection yoke is now 1.5 to 2 inches further back from where it used to be positioned. Tony do you remember if you made any changes to reset the deflection yoke?
The other is arcing that looks like lightning across the sky between the inner old plastic cover and the dag coated crt. In my case I have grounded inside and outside of the plastic cover. I also grounded the crt's dag. The charge builds up, discharges then does it again. How large is the diameter of the hole you drilled for the HV anode lead? If I enlarge the hole I already have , I'll start cutting into the plastic cover's ribbing.
A few pictures of the first tests tonight. I think all three color guns are working. When I tested this crt a few months ago the green tested the weakest.
If anyone has encountered the same issues, please feel free to chime in.
Thank ,
Ed

I would try un-grounding the dag on the crt and let the grounded dag on the outside of the plastic shroud act as the HV smoothing capacitor.

Thanks Bob, your suggestion worked. :thmbsp: A big improvement.
Ed

I ended up removing the inner 1/2 inch circular deflection coil stop. Had to cut it flush to the inside surface. This allowed enough space for the deflection coil to slide through and seat all the way against the crt neck. I drilled a hole 3-7/8 inches inward on each side from the covers' rear. The holes were kept along the same horizontal plan as the existing slots for yoke adjustment. I cut some 1/4 inch thick plastic spacers to fill the gap between inside housing and deflection coil clamp bracket. The trickiest part was placing a washer and nut on the inside end of each adjusting screw. I didn't want to drop them in the yoke or crt housing.:nono:
Two of the pictures below show the longer bolts I installed to extend the plastic housing rearward about 2 inches. I used 1/4 inch thick plastic sleeves as spacers over the four 1/4-20 hex head bolts. The upper two bolts are 4 1/2 inches long and the lower two are 4 inches long. The shorter bottom are to leave more clearance for the chassis.
These modifications made it possible to get the convergence coil assembly in the correct location on the crt neck.
I have yet to deal with purity and degaussing the screen, it's really bad. I also have to get the chroma circuits going yet. There seems to be no color, I'll try a new crystal before I get carried away.
Ed

Excellent job so far Ed! You took the adaptation to another level than what i did and after seeing your results, i will be making a few changes on mine. This thread is going to help others who are in the same boat as we were because as far as i know there isn't much out there on this problem as far as the CTC 5 goes. I'm looking forward to seeing the end result of your restoration.

If you were really able to get the yoke flush up against the bell, it only needs to be pulled back a little to fix the purity. Great work so far. Onward!

Ed, Quite a creative solution. If I understand your posted photo below, I assume you cut off the heads of the bolts screwed into the rear of the mask. Or did you find double ended threaded screws? Nice job.

-Steve D.

In picture below, the top short bolt is the original hex head type I removed. I replaced with longer ones like below. I used die to increase the threads an extra inch or so. I could have used fully threaded new bolts also. I removed the entire plastic CRT mask to replace the bolts. They are seated in hex holes on the face of the mask. I use a little tape to keep them from falling out when re-installing the mask back in the cabinet.
I've done all the modification work with the cabinet laying face down on a quilt/ pad.
Ed

Ed, Thanks for the explanation. You really thought this through.

-Steve D.

Over the last few weeks I was able to get the chroma circuits working marginally. They could be better. I found the original, from 1957, 3.58 mc crystal to be dead. I installed a newer crystal. This set uses color killer and color burst pots, which seem to have no effect on turning off the color. The color signal passes through anyway.
I extended the black plastic yoke spacers. This made it easier to draw the yoke inward or outward and install the thumb screw nuts.
After I got the color working I had to get back to the issue of color purity. No matter what I did adjusting the yoke, convergence coil assembly, blue lateral magnet or purity rings ; I was unable to get a total red screen. Last weekend at the WARCI in Madison, VK member IsthmusTV, suggested I re-install the original purity magnets as a solution. It ended up that in my case the six original purity magnets got me to a far more consistent red screen. The three magnets on the left side of the screen had the greatest effect. The three right side magnet needed almost no adjustment. Thank you Clark :thmbsp:. The fine convergence adjustments for this set leave a lot to be desired. When my wife and I return from the Columbus Zoo and ETF Convention,I'll get back to this set again.
Ed

The asymmetry of the pure red is really odd. Did you do a thorough degaussing both from the front of the tube and the back (in case any of the mounting hardware is magnetized)?

If you do degauss it again, retract the edge magnets first, so that you don't bake in an opposite field in the tube.

Regarding the dynamic convergence, I found that it is critical to get the right spacing of the neck hardware (convergence coils and purity rings) - unfortunately, you may not be able to see the location of the convergence pole pieces if the internal dag covers them, and the service info doesn't give you any measurements of the proper spacing, so then you need to experiment, making a first guess based on the illustrations in the manual.

I’m probably talking out my butt, but have you examined the magnets thenselves? Ive learned they can break and cause bad things to happen.

It looks like you're making great progress on the CTC-5.
Did you just push the magnet adjusters or turn them too? On my CTC-2B, 4 and 21AXP based moto you can push/pull the 6 front purity adjusters for coarse adjustment and twist for fine adjustment...I did not need them on my 21FBP converted sets, but the CTC-2B did, and I found twisting them to be the best way of minimizing impurities.

I should have room in the truck for that test jig you want. I can bring it to the ETF for you if that is alright by you.

Tom, It would be better for me if you don't bring the test jig to Ohio. I can pay you for it there. I can wait till the next WARCI meet we're attending to bring it home. I wanted to leave space in my car for other stuff on the way back.
Ed

Nice progress, Ed. I think you're getting very close :thmbsp:

Have a great time at the convention!

-Clark

Sounds good.

Tesla Coils Ebay
 

Guys,
Here is an unbelievable deal on a TESLA COIL that will do the gas test as described. It's so cheap it's hard to believe they can sell it for this amount. I have tried them and they work well. I bought 3 just in case one breaks and put it in a plastic project box to use as a piece of test equipment. here is the address: https://www.ebay.com/itm/15KV-High-V...19.m1438.l2649

Hope you guys can use this,

Dennis

I pulled this quote from an old CTC-5 thread of Dave May in 2013. The quote is from Old TV Nut.----

" If the drives required for the red and blue guns were equal to make white, then the pattern would need to be elliptical, with the B-Y gain = 2.03/1.14 = 1.78 times the R-Y gain. (These are the ratios dividing the B-Y and R-Y axes before the chroma is modulated.) However, the red phosphor in the early tubes is weaker by about the same ratio, so equal (approximately) is correct (that is, the pattern is circular).

By a fluke of changing both the green and red phosphors in later tubes, the red gun requires less drive to make white; so there was a fix to reduce the red luminance drive; and at the same time, the yellower green sulfide phosphor means that the extra R-Y drive is still needed, to approximately compensate by making the difference between reddish and greenish colors greater. So, the matrix adjustment does not have to change, and can stay with a circular pattern when a new CRT (e.g., 21FBP22) is substituted. "

I was wondering if anyone has a schematic or an idea of which components were altered for the reduction in the red drive? I already found the contrast/ brightness fix schematic for the 12BY7a video cathode modification.
Thanks,
Ed