verticle problem

[timmy]

hey all, im working on this 48 motorola table top 7 inch , but as you can see this is a scope 7 inch crt. i went over all resistors unless i missed one but i dont think i did but these lines and rolling i cannot find whats going on here. i subbed tubes and changed resistor values around on the vert hold and vert size but no luck. if i shorten the pic top and bottom with the vert size it will become better stable but i cant widen the screen up and down because it goes crazy. any ideas where i might look as i probably missed something here. these lines may not be there and then they come right back and the longer i leave it on the worse it gets. i even tried another vert pot and vert size pot nothing changed. would something possibly in the IF section do this because upon getting it going for the first time i had nothing, no sound or picture until i rotated the pot for channel 3 and i got picture and the sound but had to rotate a different pot to get the sound good. thing here is there is an old piece of paper tape that had writen on it " if dead" so i dont know if this was an existing problem or not and then i got it with the IF problem. this is why i am wondering if an IF problem would give these lines. one other thing, does anyone here know how to read mics colors, i got a mica that has , red, green , brown , colors ?

[Username1]

You have to look on here, or the net to find the mica colors.....
If there was a bad if section you most likely would get no picture.... Find a
tv block diagram this will show signal path.... Those pronounced lines are
most likely some interference into the vertical osc. or output stage.
You will have to look at the possibility of using a scope to figure out what
is getting in there.....

.

[ChrisW6ATV]

That curved/trapezoid look makes me think the CRT could have a physical problem with one of the vertical deflection plates.

[Eric H]

Did you recap the set? Didn't use any 6Kv Ceramic caps in the Vertical did you, those are known to cause problems in that circuit.

[timmy]

These lines are present with both scope crt and a black and white tube and the lines and the rolling seem to stop then start up again. And yes I did recap the set and all the 6kv caps are from just radios no ceramics. Maybe the Micas in the vertice are bad I'll have to consider that are probably bad and change them . Unless there is leakage from somewhere causing this.

[timmy]

this pic of the green 7jp1 is the one i refer to in another post where the brightness up between scenes i get these lines but if i lower the bright the lines wont come back. there has to be a reason for this and at this point i cant find whats going on here. my other set dont do this, but its like if the bright being up its taking something from the verticle and causing it to collapse alittle bit. im lost.

[timmy]

This set has been totally recapped all caps for verticle and horiz. The problem I have is that this set had a 2.5 meg resistor in the bright circuit off the bright pot where a 1 meg resistor belongs and putting the right resistor in makes the lines worse. And the kicker is this wrong resistor was factory , looks like it's been there for 50 years the solder joint look the same as all the others. Maybe there was a screwup when it was wired and this was done to send it out quick, I don't know.

[teevee]

Retrace lines? There are articles on adding retrace blanking circuitry to these sets, only takes a few parts... I'll see if I can find that info again.

[timmy]

i already did the retrace mod.

[Phil Nelson]

Originally Posted by timmy

does anyone here know how to read mics colors, i got a mica that has, red, green , brown , colors ?

This page describes one mica color coding scheme:

http://www.tpub.com/neets/book2/3g.htm

Different schemes were used, but this is a common one. First four dots, reading in clockwise order, are: type, 1st digit, 2nd digit, multiplier. In the example given on the page, white-brown-red-red means mica, 1200 pf.

Phil Nelson

[timmy]

Ok thanks, but I'm good now since I changed the Micas that were thought to be bad. Now I'm trying to figure out why these lines appear when the brightness is up.

[Tubejunke]

My friend, if your set plays fine other than vertical retrace lines when the brightness is set too high; I would leave it alone. A lot of early sets had retrace lines I imagine from the factory. This is acceptable performance for what you have if manageable.By manageable I mean that you can pretty much get rid of them by a picture adjustment at user level. The circuitry generally wasn't all that refined in the average consumer set of the say 50s. We must remember that the technology of the times for television was really new.

Yeah, I'd turn down the brightness, button it up and sit in a chair and enjoy!

[timmy]

problem is these lines are not retrace, the common retrace lines that come with these sets i had already but i since done the mod with the cap and resistor and that eliminated all the retrace lines. but if you look at the pic above these are not retrace lines. i have another set that dont have this problem , but its obviously got something wrong here but that is not right having to kill off lots of brightness to not see these lines since i have a crt that performs like new , why waist the brightness to hide a problem.

[Eric H]

From the picture you posted above I would say you have a severe vertical linearity issue.

I would recheck cap values and resistor values in the vertical sections to see if you have something out of whack.

[timmy]

well all the caps were done in the verticle the screen adjusts good the way it supposed to be but if the screen scene changes where there is little there to see like only a top bar showing whats on that stuff shows but not befor it pulls down alittle and there it is. otherwise the picture is fine but some scene changes will pull it down alittle to show the lines. its really weird everything has been checked and changed. some resistors are out alittle bit but nothing to do this.