Swapped CRT and a ?

[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

[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.