Black line at the top of screen? What is it??

[Magnavox300]

I have been enjoying my new Magnavox 21" B&W,
thanks to everyones help here.

A new black line, with some white dashes just appeared at the top of the screen when I am watching DVD's.
Tried the Vertical Hold at the top of the set,
and right before it dissapears, the vertical goes out of sync.
I tried adjusting the vertical height at the bottom of the set,
and I can get rid of it, but then a white glare comes up from the bottom!
Any ideas?
Thanks!

Magnavox300

[radio nut]

only dvd's, how is cable tv on this set?

[Magnavox300]

Originally Posted by radio nut

only dvd's, how is cable tv on this set?

Only DVD's.
I actually gave up regular TV years ago.

[David Roper]

The height interacts with vertical linearity control, did you try adjusting both? You might also measure the line voltage where the TV is plugged in. If it sags, the picture will shrink. Usually shrinkage at the sides becomes evident first, but it would be good to confirm it's at least 115.

[old_coot88]

Try the centering rings on the back of the yoke. Should be able to nudge the whole raster up a bit.

[miniman82]

You're seeing the very top of the raster, which also means you're seeing a part of the picture that's normally out of view. As I understand it, the first few lines of the video signal were repurposed to add text or other info. It shows up as dancing white lines. To get rid of it, you need to play with vertical height, centering and linearity. First center the raster in the middle of the screen, then use the height pot to overscan the CRT face slightly. Lastly, adjust the linearity pot so the raster is uniform top to bottom. This is best done with a crosshatch pattern on the screen, but you can eyeball it with off air images.

[Magnavox300]

Thanks!
It is almost perfect, centering rings got rid of most of it,
now I will adjust the vertical linear and height to make it just right.
Thanks to everyone for all the expert information!

Magnavox300

[DaveWM]

let it warm up at least 15 min before making any adjustments.

[Chip Chester]

It's the analog closed-captioning data, on line 21 of the vertical interval. Normally blanked, of course... Line 21 is sposed' to be the last unseen line before active picture.

Chip

[Jeffhs]

If you were viewing broadcast TV and saw these lines, dots, etc. at the top of the picture they would be what are known as Vertical Interval Test Signals (VITS). These show in the vertical blanking interval and are (or were) used to adjust such things as video levels and so forth. These signals, when seen in the blanking interval of non-broadcast images such as those from DVDs, however, are, as has been noted, for text, closed captioning, and other advanced functions of today's TVs. Some GE televisions of the '70s had a feature known as "VIR", which was supposed to automatically control hue, brightness, saturation, etc. of a color picture according to a signal sent by the broadcaster in the vertical blanking interval. I do not know if the VIR signal was ever visible in the blanking bar, in addition to network VITS or otherwise.

VITS are still used in broadcast TV today, but are normally invisible to viewers since the blanking bar is ordinarily off the top of the screen on properly scanned TVs, as were the older versions of these signals. The signals are likely used for closed captioning, text, etc. as they are for DVDs and other non-broadcast applications.

The "white glare" at the bottom of your TV picture when you are trying to adjust vertical height and linearity is called foldover. It occurs when these controls are incorrectly set (normally far too high) such that the lower part of the image on the television screen is actually, literally, folded over onto itself. The cure is to adjust the height/linearity controls so the picture just overscans the CRT mask at top and bottom. Since these controls normally interact with each other, you may need to fiddle with the adjustments (trial and error) until you get the desired result.

[Penthode]

Originally Posted by Jeffhs

VITS are still used in broadcast TV today...

Alas. VITS is no longer broadcast. Analog TV broadcast included the vertical blanking interval to carry data such as VITS, Closed captions, Nielsen data etc. But DTV does not accommodate carriage of the VBI or vertical blanking interval. Only the active picture is broadcast with the ancilliary data carried as separate data packets ins the digital broadcast stream.

DTV receiver boxes and DVD players recreate VBI signals from the ancillary data. This is to provide a backward compatibility with older analog TV.

So we can now say V.I.T.S. - R.I.P.

[Boobtubeman]

Had a 1977 Mot Ward with VIR only a 19 inch and $400 back then..

The last tv repair shop here in town closed months ago.. Not goood....

I seem to recall a cartoon in the local paper here years ago with a pic of a repair shop and a tv with a hand holding a screwdriver punched through the face of the CRT from the back with a one worded caption "DAMN!"

[Eric H]

It looks like the height is too short to me, if you can't easily adjust it out try a new Vert Output tube.