68kMLA Classic Interface

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Color Classic line across screen
Posted by: chiptripper on 2022-06-22 22:23:09
So I've been fixing up a trio of CC. I have a strange symptom that I can't sort out. There's a horizontal line about two thirds of the way down the screen. It's very faint and honestly not a big deal, but I'd like to fix it if possible.

At first I though it was just an anomaly, but this same line has shown up on both CCs I've fixed so far. (I have no idea if it pre-dated my refurbishment, they were both dead when I got them.)

Voltages are good, screen pots are adjusted, fresh caps on both logic and analog board. Computers run great and the screen is otherwise nice and bright. Any idea why I'm seeing this?

(Challenging to take a decent photo but I've attached one. The line is much more apparent IRL.)
Posted by: chiptripper on 2022-06-22 22:27:26
Ah. Just did a little more digging and I've seen it suggested this is just a normal Color Classic thing, a wire inside the tube. Is that correct?
Posted by: Chopsticks on 2022-06-22 22:29:10
yup, its more specifically a part of the Trinitron screen design, larger trinitron screens will even have a second line a 1/3 from the top.
Posted by: chiptripper on 2022-06-22 22:37:45
Oh neat! I fixed a vertical line on a Classic not long ago by replacing PP1 (thank you Larry Pina) so I wasn't sure if this was something similar, good to hear it's normal.
Posted by: Chopsticks on 2022-06-22 22:52:41
I think they are called sstabalizing wires or something like that, as far as a know only trinitron displays have them. being that TV's used interlaced signals back then they tv geometry was more often or not factory tweaked so that the lines would be hidden in the scalines of the interlaced NTSC/PAL signal being displayed.
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