CTC-4 Director 21

[Phil Nelson]

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

[SwizzyMan]

Originally Posted by Phil Nelson

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.

[jr_tech]

Originally Posted by miniman82

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.

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 ?

just curious,

jr

[miniman82]

Originally Posted by jr_tech

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?

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.

[SwizzyMan]

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

[DaveWM]

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.

[MRX37]

Tube's probably fine, just a bit weird.

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

[SwizzyMan]

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.

[MRX37]

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

[SwizzyMan]

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

[jr_tech]

Originally Posted by SwizzyMan

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

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

[Tubejunke]

Originally Posted by jr_tech

Perhaps there is some arcing that is causing the interference?

My thoughts exactly as I looked at those screen shots. I’m by no means a color TV expert, but I do have a Zenith roundie that had the slightest arching in the HV cage. It was hardly audible, but that was exactly what the picture looked like. Turned out that the HV rectifier socket was fried. Replaced that and no problems. In addition, I think that set needs degaussing. Most of us aren’t lucky enough to have a real serviceman’s degaussing ring, so I just use my Weller soldering gun in the same manner that you would use the ring.

[Electronic M]

Originally Posted by Tubejunke

My thoughts exactly as I looked at those screen shots. I’m by no means a color TV expert, but I do have a Zenith roundie that had the slightest arching in the HV cage. It was hardly audible, but that was exactly what the picture looked like. Turned out that the HV rectifier socket was fried. Replaced that and no problems. In addition, I think that set needs degaussing. Most of us aren’t lucky enough to have a real serviceman’s degaussing ring, so I just use my Weller soldering gun in the same manner that you would use the ring.

I've got a real service degaussing coil and I've made spares....Allz you have to do to make one is find a decent sized 20" or bigger BPC set at the curb, steal it's degaussing coil, loop that 3 times around so it becomes a smaller coil ~12-14" in diameter, wrap it in electrical tape so it holds that form, and attach a cord.
...It will get hotter faster than a servicing coil, but one can get about a minute run time (plenty for most sets) out of it before it needs a cool. I made a thread on the process a while back.

[Electronic M]

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.

[old_tv_nut]

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)