White Lines

[VA561]

I have a 1950 philco, model 50T-1404. The set runs great except for about 5 or 6 annoying diagonal white lines that will not go away. They are thin lines that remain no matter how I adjust the brightness/contrast. They start from the top right corner and go to the bottom left. When I start to turn the vertical adjustment knob, the lines will move before the picture starts to roll. If I move the vertical up slightly the lines move up. If I turn the knob down , the lines move down. Except for this annoying problem the picture is great. Any advice would be greatly appreciated.

[mbates14]

they look like retrace lines.

[Eric H]

These look more like the lines you get from having the brightness turned up too high rather than the ones from Macrovision which are usually only at the top.

It's hard to tell from a screen shot but that picture looks either too bright or not enough contrast.

Do the brightness and contrast controls work correctly, in other words taking the picture from completely washed out to overloaded or completely dark to way too bright?

A weak CRT can cause retrace in some cases, something weak in the video circuits can do it too.
The blanking pulse comes from the Vertical circuit i believe so a problem there can cause a problem.

What has been done to the set as far as electronic restoration?

[Dan Starnes]

What Eric said..

[Tom Albrecht]

Retrace lines are a common problem in 1940s and 50s sets, and do not mean that the set is maladjusted. There is different signal content in the retrace interval today than when these sets were designed. Various circuit modifications can be used to improve the situation. Here's an example of one of the more complex, but very definitive, cures for this problem:

http://www.antiqueradios.com/forums/...ic.php?t=86186

Often a simpler modification of feeding a suitable sawtooth waveform from the vertical deflection circuitry through a small capacitor to either the cathode or grid of the CRT will work pretty well. If you search on "retrace lines" at ARF (and maybe here too), you can find information on some of the simpler fixes.

[jr_tech]

So how is the blanking pulse generated in the '1404? I don't see an obvious connection between the vertical output and the CRT.
Note:
1. The end of the brightness control just goes to B+
2. wire from r-53 goes to sync amp.
3. wire from contrast control goes to video detector and sync sep.

jr

[VA561]

I bought the set from a collector who said that he had recapped the set and replaced all weak/shorted tubes. He did make the comment that sometimes the signal from a dvd player is to strong for an older tv and he has had good results using a vcr. When I read some of these posts, it is a reminder to me that I am just starting to learn about tv restoration!

[mbates14]

hey you know, we all gotta learn somewhere.