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