Horizontal Lines at Top of Robotron Screen

Ok. I've been watching some videos and doing some reading, and I have a theory. Tell me if this makes sense. I won't have time to test it until at least Friday.

The chassis was re-capped about a year ago. I have the vertical position pin (no pot) in the UP position, and the screen is still too low. Several of you said the horizontal lines are usually hidden, but can show lower on the display due to foldover.

Here's my theory: My yoke needs adjusting. I remember seeing two wedges lying loose in the bottom of the cabinet. If the wedges fell out (or weren't installed), and yoke has the image positioned too low, that could explain the fact that I can't get it high enough on the screen, and the foldover, could it not? To add to my belief, the image is slightly angled; just a tiny bit lower on the left than the right.

Thoughts???
 
Yes, that could certainly be it, probably not the foldover, but definitely could be the position issue (IMHO).

Ok. I've been watching some videos and doing some reading, and I have a theory. Tell me if this makes sense. I won't have time to test it until at least Friday.

The chassis was re-capped about a year ago. I have the vertical position pin (no pot) in the UP position, and the screen is still too low. Several of you said the horizontal lines are usually hidden, but can show lower on the display due to foldover.

Here's my theory: My yoke needs adjusting. I remember seeing two wedges lying loose in the bottom of the cabinet. If the wedges fell out (or weren't installed), and yoke has the image positioned too low, that could explain the fact that I can't get it high enough on the screen, and the foldover, could it not? To add to my belief, the image is slightly angled; just a tiny bit lower on the left than the right.

Thoughts???
 
Yes, that could certainly be it, probably not the foldover, but definitely could be the position issue (IMHO).

Right, but the folderover could be caused by me expanding the image vertically and putting it in the UP position, to try to make it display properly, could it not?

Grasping at straws. If I'm barking up the wrong tree, say so.
 
Update:

I gave up. It seems I either have annoying lines, or convergence problems. I can't seem to find the happy medium.
 
This same thing happened to me on my Robotron when I tested a different (newer) Wells monitor.

However, I was able to adjust the vertical pot and effectively "push" the image high enough to hide the glitchy line.

Not sure why the older (original) Wells monitor didn't do this. (Or maybe it always does this and that monitor was adjusted to hide the line as well. )
 
This same thing happened to me on my Robotron when I tested a different (newer) Wells monitor.

However, I was able to adjust the vertical pot and effectively "push" the image high enough to hide the glitchy line.

Not sure why the older (original) Wells monitor didn't do this. (Or maybe it always does this and that monitor was adjusted to hide the line as well. )

When I get everything else in my game room fixed, I'll address this. Meaning, I'll probably never address this! :) It's just a bit of an annoyance, and I'm probably the only one who notices.
 
I'm pretty sure if your monitor's height can be adjusted just right, you can get the lines to project offscreen. It's just a matter of setting the monitor up just so.
I have a Joust with the lines, but they move closer and closer to the top as the monitor warms up (I'm hoping a cap kit will make it strong enough to move them past the top of the screen...)
 
if its a 4900 it'll do that, it develops the squish/foldover thing like Nintendo monitors. I adjust them off too, but it's a natural feature. I shared the Sean Riddle article because it explains why it does it.
 
2 things.

This is common with K4900's as there are a few revisions of the board and they use different yokes. Not totally different but different enough to cause that foldover. If you have other k4900's try swapping chassis.

Also, I capped a 4900 in a Tapper a long time ago and after the cap job it developed a foldover at the top. I want to say that the kit had me install the wrong cap at C311. The kit had a 10mf whereas the board had a 4.7mf cap. The 10 caused a foldover so I put the 4.7 back and all was right.

At least I think thats the cap number/value.
 
subscribing. I have this effect on my stargate but not on robotron so may be motivated to go check monitors and adjustment.
 
It's definitely the monitor. It is a K4900. The yoke is wedged at a downward angle and the screen position is adjusted all the way up. If I adjust the yoke to center the screen I can get rid of the lines, but I can't get the convergence at that point; either dead on at the top and off on the bottom, or vice versa. That's why I opted to just leave it like it is. No big deal.
 
why are you even touching the yoke for a vertical size adjustment?

I wasn't. I was trying to adjust the image position. The vertical size/position was up so high it was rolling over, causing the lines (so the theory goes) By adjusting the yoke, I was able to reposition the image so I didn't have to adjust the image size/position on the chassis as high as it would go. It removed the lines, but I couldn't get the convergence satisfactory.

Like I said, no big deal.
 
you know when converging that the two inter most rings should adjust the "guns" location on the tube so you can move the entire image up down left or right. this is usually done in the first stage of convergence when aligning the yoke to the tube. bring up a blue screen and then adjust the yoke so the entire image is blue and then you can move the image around on the screen, usually to bring the guns into "color focus" this being where the screen is fully blue and not bleeding into other colors due to the yoke alignment. After this adjustment is made then the Guns are "centered" and the rest of convergence can be carried out.
After the blue, check the red, and then the green for purity. I believe this is the Purity stage of convergence.


I hope this make sense.
 
you know when converging that the two inter most rings should adjust the "guns" location on the tube so you can move the entire image up down left or right. this is usually done in the first stage of convergence when aligning the yoke to the tube. bring up a blue screen and then adjust the yoke so the entire image is blue and then you can move the image around on the screen, usually to bring the guns into "color focus" this being where the screen is fully blue and not bleeding into other colors due to the yoke alignment. After this adjustment is made then the Guns are "centered" and the rest of convergence can be carried out.
After the blue, check the red, and then the green for purity. I believe this is the Purity stage of convergence.


I hope this make sense.

Yes, thanks.

The reason I played with the yoke is because the wedges were lying in the bottom of the cabinet and the yoke was all the way down against the top of the neck. I wasn't sure if it was supposed to be that way or not. After working with it, that's where I get the best convergence, and the lines are still there.

Like I said, it's ok. I've put enough hours into it, even if I was doing it wrong. Don't care. The lines are fine.
 
Yes, thanks.

The reason I played with the yoke is because the wedges were lying in the bottom of the cabinet and the yoke was all the way down against the top of the neck. I wasn't sure if it was supposed to be that way or not. After working with it, that's where I get the best convergence, and the lines are still there.

Like I said, it's ok. I've put enough hours into it, even if I was doing it wrong. Don't care. The lines are fine.

Im not talking about the yoke, but the rings. the yoke is just part of the process. you could likely move the whole image up using the rings not the yoke.
 
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