Zenith 2250R

[Zsuttle]

So, I was messing around with the TV and letting it run for a little bit. Lost the vertical hold from a few resistors soaring in value. Fixed that, but still can't get a crisp picture from this set. I can adjust the focus magnet to get a pretty good image, but it sorta stops at a point. Any ideas?

Also, anyone know where I can obtain test picture tube? Brushing up against the CRT isn't my definition of fun. I haven't seen any round versions on the Bay recently.

[Kevin Kuehn]

Do you have the brightness most of the way up? If so it could be that the CRT is near the end of it's useful life, which at that point the electron gun looses it's ability to focus well. It's also dependent on HV, so it could be that your HV is still on the low side. Try dimming the room lights and see if bringing the brightness down helps sharpen the picture any.

Another thought is if the ion trap is on the neck reversed end for end it could be limiting your overall brightness.

Considering the amount of ambient lighting in your shop I'd suggest your CRT is doing it's level best at producing a decent picture. These early tubes were never intended to be watched in a well lit room. The screens simply can't produce a high enough level of contrast with the brightness turned up high. Just remember that the CRT face can only go as dark as the ambient light reflecting off it's face. In other words the CRT can't make it self go any darker, it can only lighten up. That's ultimately what limits your contrast. Hope that makes sense.

[Zsuttle]

Originally Posted by Kevin Kuehn

Do you have the brightness most of the way up? If so it could be that the CRT is near the end of it's useful life, which at that point the electron gun looses it's ability to focus well. It's also dependent on HV, so it could be that your HV is still on the low side. Try dimming the room lights and see if bringing the brightness down helps sharpen the picture any.

Another thought is if the ion trap is on the neck reversed end for end it could be limiting your overall brightness.

Considering the amount of ambient lighting in your shop I'd suggest your CRT is doing it's level best at producing a decent picture. These early tubes were never intended to be watched in a well lit room. The screens simply can't produce a high enough level of contrast with the brightness turned up high. Just remember that the CRT face can only go as dark as the ambient light reflecting off it's face. In other words the CRT can't make it self go any darker, it can only lighten up. That's ultimately what limits your contrast. Hope that makes sense.

When I do most of the adjustments, I keep the lights down, I’ve found that the fluorescent lights are way too bright, but that a light on in the back isn’t too bad. Brightness isn't bad, I have it up at about 3/4 brightness. Any more and the image washes out. The HV is still running lower than spec. (still 7.5kv) I replaced a bunch of resistors in the both the horizontal and vertical sections to fix a few issues. I’m gonna try injecting a composite signal tomorrow to see where that gets it. Hopefully it’ll make it easier to make adjustments that way. Also, is there an easy way to tell which way the ion trap goes? I don’t think the one on the unit is stock, and it doesn’t have an indicator.

Originally Posted by Electronic M

One of the 8" rectangular test tubes with the same base (8AXP4 IIRC) will work on the early sets, but the screen will not be filled due to the difference in deflection angle.

Ok, great to know. Murphy’s law, there’s none listed right now. I’ll keep a look out

[Eric H]

Originally Posted by Zsuttle

I can adjust the focus magnet to get a pretty good image, but it sorta stops at a point. Any ideas?
.

When you say adjust the focus magnet are you adjusting the focus magnet itself or the focus potentiometer?

[Zsuttle]

Originally Posted by Eric H

When you say adjust the focus magnet are you adjusting the focus magnet itself or the focus potentiometer?

Focus magnet, to my knowledge the H22 series only has mechanical focus.