Swapped CRT and a ?

[Dan Starnes]

I put the ion trap on and messed with it. Worked well at the 12 oclock position and slid all the way back, so it is there. Would not work any farther forward. Tv is working very well. And I forgot to see what the make of the CRT was dangit. Another cell phone pic, my digital was not charged.

[wa2ise]

Originally Posted by Dan Starnes

I put the ion trap on and messed with it. Worked well at the 12 oclock position and slid all the way back, so it is there.

Does it work any better than if it's not used at all? If it doesn't work any better than when it's not used, then it's not needed and you should take it off.

[Dan Starnes]

The centering is better, could not really get to where I thought it should be before the ion trap. Also prior to the ion trap installed I noticed a slight cone head in some scenes, now that is gone and my height control is in the middle of its setting. Basically I had to adjust the centering, height and vertical, and I have a very very nice picture.

[jeyurkon]

I guess I have to throw my hands up in the air. I can't tell from the photo which type of gun it is.

There are two possible orientations for the trap. It might have markings on it indicating which side should be facing forward, or it might not. If it doesn't you might have to try both orientations.

Here is one datasheet for that CRT. http://tubedata.milbert.com/sheets/093/2/21XP4A.pdf

The fact that the centering is easier is encouraging. Maybe someone else is more familiar with 21XP4A guns.

John

[leadlike]

It looks like your crt gun has an electrostatic focusing element-did they make any bent gun tubes with electrostatic focus? I thought ion traps went out of style around the same time magnetic focus did.

[jeyurkon]

Hopefully the last of my unhelpful comments.

This would be simple if we knew the CRT wasn't rebuilt because it would almost certainly require an ion trap. It's more complicated because a re-builder could have used a straight gun.

1. It could be a straight gun and the trap isn't required and only works when the trap is mounted out of the way. The washed out images were due to scattering off of an electrode.

2. It could be a bent gun and the trap is required. Having a raster without the trap would require that the CRT had been operated at high brightness without the trap and the beam then burned a new exit hole. Unfortunately, this is a possibility. With the trap in place it works better, but if there is an exit for the electron beam without the trap, the ions will still be able to exit that way with or without the trap.

There's still the possibility that you have the trap flipped the wrong way, but that doesn't change above scenarios.

leadike: It is electrostatic focus.

John

[jr_tech]

Originally Posted by leadlike

It looks like your crt gun has an electrostatic focusing element-did they make any bent gun tubes with electrostatic focus? I thought ion traps went out of style around the same time magnetic focus did.

I have seen bent guns with electrostatic focus... an example is this DuMont 14SP4 that I just replaced in a small DuMont portable from 1956 (or so). This gun has a combination of a VERY bent gun AND electrostatic focus. The gun looks like it was made in two different eras, ceramic supports and an older looking design at one end, and multiform rods and electrostatic lens at the other! The gun had the worst looking welds that I have seen in a CRT and was indeed OPEN at the cathode sleeve weld. The weld at the 1st anode (shown in the picture) was quite carbonized and fell apart when I touched it!

jr

[andy]

...

[cbenham]

Maybe I missed it but I think no one has mentioned something that might be important about the placement of the ion trap. The owner of the TV shop where I worked after high school had me pencil-draw an arrow on the ion trap pointing forward toward the screen before removing it.

If you get the trap on backwards, this makes the magnetic polarity wrong and the trap won't operate correctly. Don't know if this is what's happening here, but thought I'd mention it.

Hope this helps, Cliff

[Dan Starnes]

Thankyou all for the very helpful info. I have learned alot. The gun is straight and sorry for the low quality cell phone pic. I did turn the ion trap around before being satisfied, but no difference. When I was messing with the ion trap I could make the picture bend and in other positions it would not make a good picture. It did result in a sweet spot where it is now located. The tv has never performed better, picture quality wise, and I cannot complain at all about quality. I am picky when it comes to sound and picture quality.

[electroking]

Originally Posted by leadlike

It looks like your crt gun has an electrostatic focusing element-did they make any bent gun tubes with electrostatic focus? I thought ion traps went out of style around the same time magnetic focus did.

The 21ALP4A in my Viking (Eaton's of Canada brand made by Electrohome)
is electrostatic focus with ion trap. TV is from 1956 as far as I can tell.

[andy]

...

[eberts]

That is a straight gun with the focus hooked to G2 internally, remove the ion trap and leave it off.

[jeyurkon]

Originally Posted by Dan Starnes

Thankyou all for the very helpful info. I have learned alot. The gun is straight and sorry for the low quality cell phone pic. I did turn the ion trap around before being satisfied, but no difference. When I was messing with the ion trap I could make the picture bend and in other positions it would not make a good picture. It did result in a sweet spot where it is now located. The tv has never performed better, picture quality wise, and I cannot complain at all about quality. I am picky when it comes to sound and picture quality.

I'm not sure I understand. Did you end up leaving the ion trap on or off? In either case, I'm glad it's performing well for you.

John

[jeyurkon]

Originally Posted by eberts

That is a straight gun with the focus hooked to G2 internally, remove the ion trap and leave it off.

Which CRT are you referring to? That doesn't seem to match the data sheet for any of the CRTs mentioned here, unless I missed one.

John