CTC-4 Director 21
 

just picked up this nice CTC-4 director down in West Palm. The set has a big history and has been heavily modified. This set originally came from Connecticut. It was acquired by its previous owner (he was a repairman) when a customer decided that the set was too expensive to get repaired and they left it. It eventually moved down here to Florida. The previous owner was an experienced Ham radio operator. I was invited to take a look around his house while we were picking the set up, his house was full of receivers and a couple FM transmitters he built himself with many other pieces of tube equipment. I originally heard about this set through my wanted ad in the classifieds here. The original price was $6000 BIN and $3000 to bid on it. Eventually, it made its way to $500 after I offered $500 for it. The first thing that I noticed when i saw it on ebay was that it had a glass 21FBP22 instead of the original 21AXP22 crt. This didnt bother me much at all. While it may decrease its value, the FB will have a much better chance of surviving all these years without leaking. I was able to test the CRT today and the results were a bit discouraging, the cutoff on almost all the guns was just barely under the box on my CR-31A, and to make matters even more confusing each gun tested fine for a few seconds on the tester, but then the needle starts swinging erratically and upward. I thought I read somewhere that these results may indicate a gassy tube, but this doesnt make any sense since I can get a full raster, but the tube seems kind of dim and the red color seems to the least bright of the three colors. I'm not sure if I should zap the three guns with a rejuve or what. I ran the set for about five minutes monitoring the current draw just so I could get a baseline. I got a decent black and white picture, but when I turned the color on I got a lot of interference in the form of small streaking horizontal lines. I also noticed the colors are pretty rough with no signs of light blue and pretty dim reds. At the end of the five minute run I heard a loud pop (sounded like a firecracker).Current draw stayed fine. I immediately shut the set down. I think a paper cap finally gave out causing the loud pop. This is going to be a long project , but I think I can handle it.

More photos

you should Discharge the HV from the CRT completely before testing on a CR-31, this would cause Erratic Testing, the pop you heard could have been a HV discharge to chassis Ground since its been modified for a newer tube, I went thru this on my ctc-4 before the CRT got rebuilt when hawkeye was in business, there is also some mods in the Gun Drive Circuit to make these newer tubes "run" correctly, color Temp is a bit different
Good Luck!

The loud pop could easily have been a HV arc from the anode button to the shield (where somebody has made a big cutout in the shield). In fact, in your 5th photo there's what looks like an arc track from the button to the shield.

"rejuvving" the jug should be the absolute last resort.

Definitely do not rejuvenate the CRT at this point. Too easy to kill the tube, and what you're seeing on the screen may be normal for a CTC-4 that's chock full of bad caps. A working television will tell you more about a CRT's condition than any tester.

I agree with old_coot88, that pop sound could be arcing, and the cutout in the CRT metal retaining ring is an obvious place to look. If you run the TV briefly in a completely dark room, you might even see the zap occur along that dark track seen in the photo.

When I installed a glass CRT in my set, I made a smaller cutout in the ring, but I also covered the nearby edges with cambric insulating tape rated for 90KV. More about all that in:

http://antiqueradio.org/RCACTC-4ColorTelevision.htm

You are right to think of this as a long term project. Be patient and it will all get done. CTC-4s don't come along very often, so enjoy working with this one while you can.

Have fun!

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

P.S. What's in the little metal project box? Looks like a relay and a tube on top . . . ?

Thanks Phil! I'll try and keep watch on that area suspect to arcing. The little project box is actually a soft start module. It lets the tubes fully heat up before applying any voltage to them. The same concept is shared on your CTC-7, but this was one of the modifications the previous owner installed. I think its pretty nifty! :D

Cant tell if this is a HOT cathode current meter or what. I dont think it is since the meter only has a range of 10 MA and normal cathode current is atleast 100MA.

It could be a cathode current meter with the appropriate shunt resistance in parallel with it to scale the current it receives to the appropriate range...

That meter is one milliamp full-scale. So it's probably wired to measure the HV regulator current. If it's measuring H.out cathode current, it'll have a low value shunt across it.
Normal H.out cathode is closer to 200 ma.

I wonder if the CTC-4 has those pesky HV issues like the CTC-5 does? I really hated dealing with that in my 5. And how is its performance? Hopefully better than my 5 too.

5 is the only one with weak HV, you won't have any trouble getting a full 24/25 KV out of this set.

I was doing another current monitoring power up to keep an eye on the possible arcing area from crt to yoke shroud/housing. I discovered something very interesting and possibly damning. There is a strange orange almost neon-like discharge between the very edge of the internal coating to the shadow mask assembly im assuming in the crt. Now I dont suspect this to be oxygen molecules since the color of the discharge is orange not purple, but could this mean my CRT is in trouble? I don't think the tube is gassy since I can still get a nice, bright and full raster on the screen. I've noticed the glow kind of likes to jump around like some neon bulbs do (like electricity in a decorative neon flame bulb trying to find the path of least resistance). This is concerning me since I have never EVER seen anything like this. Your thoughts?

Contrats! Appears to be a rather nice set condition wise. Although, I feel it's shameful that it has been butchered with an all glass tube. Just my personal opinion; as I feel that the real reason to own an early color set is to have the original rare metal crt and be able to see what an actual color picture looked like back in the day with a 21AX.

BTW: if you should decide to convert this back to the correct 21AX crt, I have a purity ring and the plastic insulation shroud from a ctc4 I would be willing to sell.

Same here, came on a spare jug I bought and I don't need it. Got the metal parts too, they aren't hacked.

As soon as I get some money. I'm buying an ax if I can even find one. I really wish I had an ax for this set. But can anyone answer my question on the reasons for the orange discharge in my glass 21FB?

Who cares, it makes an image.

I'd love to find a 21AXP22 for my CTC-4, but they don't grow on trees. Meanwhile, a glass CRT lets me watch the set. Without viewing two CTC-4s side by side (one with 21AX, the other with glass), I'm not sure my uneducated eye could tell one from the other, anyhow.

Sorry, I don't have a good guess about the orange discharge inside your CRT. What's the condition of the CRT's aquadag coating? All in good shape and securely connected to ground? Does the dancing glow move in concert with arcing sounds? Or is completely independent?

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

Is there a ground strap on the bracket that holds the crt ?
Sorry it was mentioned already by Phil Nelson .

Dag is perfect.Dusty but in nice shape. The dancing orange glow is completely independent. It only occurs on the lower areas and sometime the top areas at the left side of the CRT. While I'm no longer concerned about my CRTs health I am still wondering what this is or if it does mean trouble. I will also mention that the external graphite coating is properly grounded.

Just a very wild guess... perhaps some red phosphor from the photo-deposition screen process did not get cleaned completely off of the panel skirt. and is being excited by secondary electrons emitted from the shadow mask. :scratch2:

jr

Shouldn't be possible, the shadow mask is spot welded to a frame which has a lip on it that extends back towards the electron gun specifically to prevent stray electrons.

One last question: does the display on the screen face change in any way when the orange glow is dancing? I don't have a theory about what it is -- just curious.

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

I can't say the picture changes at all. Absolutely nothing out the ordinary with the screen brightness.

Tube's probably fine, just a bit weird.

Also the guns might "wake up" if left to run for awhile.

Interesting, I haver broken open a 21FBP22 so have not seen this lip... how far back does it go... far enough to cover the frit bead? Perhaps the frit bead is aluminized or dagged over to prevent charging and or secondary emission, or the lip perhaps covers it ? :scratch2:

just curious,

jr

Let the CRT cook for an hour. It came right up. Full steam ahead with the restoration. Already have good color picture but a lot of interference.

Well heck, you're already 90% there. Probably just needs a good recap and it'll be good to go.

Here is what I am working with. Heavy interference and bad purity.

Looks like bad alignment to me. If you turn down the color to 0, then adjust the fine tuning for best monochrome odds are a lot of that smearing/ringing will go away, and if you then turn the color back up you will not get near as good a color picture at that fine tune setting.

The alignment on my CTC-4 is total crap (thus why I put it to the side)...Color, monochrome, and sound all are at their best at different fine tune settings and there is NO compromise setting that allows two to be even decent simultaneously.

How is the dag on the outside of the CRT grounded? Perhaps there is some arcing that is causing the interference? A fair amount of surface area is needed where the ground connection is made to the dag. Learned this back in my "poor starving young engineer days" where all that we had for a color tv was a small group of 4s that were patched together well enough to sorta work on a rotating basis. One of mine got necked (sliding closet door accident) and all that I could get was a rebuilt 21FBP22. It took a bit of effort to get the jug grounded well enough to stop the interference streaks in the picture.

jr

The color bars have an obvious sound beat - so the sound trapping is definitely not right at this fine tuning setting. Does the interference dance to the audio? (hard to tell from a still shot)

Been a while since I have looked at it, but on a guess probably 3/4" or a full 1"? Something like that. This particular mask and frame assembly was from an AXP that got turned into a picture frame, but I don't think they changed anything about its construction in later tubes. Don't remember where I read about it either, but I know that the lip in there is to prevent stray electrons from reaching the screen and lighting up any of the phosphor dots.

Here's a video of what it looked like back in December of 2015. I guess alignment can go that far off after sitting dormant for 8 months? https://www.youtube.com/watch?v=O15e4R8jr8k

alignment does not go off as far as the coils are concerned unless there has been screw driver drift. I would look somewhere else. Clearly the beat pattern is prob from miss tuning of the fine tune adjustment. the other is some kind of interference.

I assume you are using some kind of RF devise for the signal, is that the same as the early example? If RF try a different channel if that is an option. Assuming you have matching transformers and good quality cable for feeding the signal.

I'm using a BT modulator. It has that horrible hum when the modulation is too high, but my other two roundies don't have the overmodulation hum in their speakers and for some reason only the 4 is humming. The fine tuning knob only turns about an eighth of a turn before I lose sync. It was originally hooked up to a dtv converter box.

...

Sometimes it is possible for the fine tuning to be so far off that the tuner is recieving while set on the next channel and/or tuned to the wrong sideband of a simple modulator.
If you are using channel 3 on the TV, try channel 4 or vice versa. If your modulator is versatile, try both one channel up and one channel down.

baluns, terminations, OTA on that channel, connections, etc...
I had one with an intermittent balun in the tuner that gave me issues once.

Just for the heck of it, try subbing the last IF tube. Ringing/smearing in the luma is a not-uncommon problem caused by the last IF tube, even tho the tube tests 'good' on a tester.

I'll switch to channel 4 and sub the 3rd IF 6AN8. Don't see why 8 months would totally mess this thing up.