Horizontal Lines at Top of Robotron Screen

TCinTEXAS

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I've got these lines at the top of my Robotron ever since I got it working. I don't see them on other Robotrons, so I don't think they're normal. I've done some searches, but can't find the exact problem. Most of the suggestions are "adjust the vertical position to hide the lines," but these lines are much lower (in the score area).

Does anyone know what causes these, and what the fix might be?

Thanks in advance.

 
I believe those are the same lines, but your vertical is folding over... Try shrinking the vertical height and you might be able to see what i mean, but a cap kit is probably a good idea to get rid of it
 
There are always lines. Perhaps your monitor needs a slight tweak. Has it been recapp'd?

Sean discusses the basics of the phenomenon here ->

http://seanriddle.com/lines.html

I read that, but wasn't sure if he was talking about the same thing. His solution seemed pretty complicated. I recapped this monitor about a year ago. It brightened it up, but didn't change the lines.

I don't know if it's related, but it's a K4900, and the image is a bit low, even though the vertical position setting is in the UP pin.

I hate to hack up the board, but may give it a try.

OK. I won't! :)
 
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I believe those are the same lines, but your vertical is folding over... Try shrinking the vertical height and you might be able to see what i mean, but a cap kit is probably a good idea to get rid of it

I'll play around with it. They only show up at certain times, like when the brains are materializing.
 
Ok, I'm confused. This entry in a very old post describes a suggested solution to the problem:

https://forums.arcade-museum.com/showthread.php?t=147325&highlight=robotron+lines+screen&page=2

O.k. I think I know the fix. It's a pain in the ass though. You would have to adjust the horizontal width to make the screen small enough where those lines would be on top of the high score. Now, the picture will be a lost smaller and as soon as you even try to increase the horizontal width those lines shift below the high score.

The fix:

Adjust the horizontal width until those lines are well above the high score. The picture will be a lot smaller and it won't fit the screen.

Next, you'll have to discharge the monitor and remove the chassis. This is a WG 4900 that I'm working with. C365 cap position is the Horiz width cap which will need to be changed to a
different value so it will expand the screen to hide those lines. The capacitor that will needs to be used is Polypropelyne (Bob Roberts sells these). The best method of testing which cap will work best with your chasssis / tube is as follows:

Make a double ended alligator clip wire. At position C365 you'll need to remove the cap at this position and solder in two posts so you could clip one alligator clip on each post. On the opposite end alligator clips you'll need to dry different size polypropelyne caps to see if the picture gets better or worse. Once you find the right cap and the screen expands properly, those lines should go away.

Here is a list of Horizontal width cap locations for different monitors from Bob Robert's page:

* Common Width Cap Positions
* Wells-Gardner K4600 Series - C615
* Wells-Gardner K4900 Series - C365
* Wells-Gardner K7000 Series - C38
* Electrohome G07 - C515

The Bob Roberts link for the horizontal width caps page is as follows:

http://arcadecontrols.com/BBBB/width.html

Now to test this method myself. However, I'm confident that it should work for all.

I don't understand how adjusting the width will affect the horizontal lines purportedly resulting from a vertical size problem. Help me out, please.
 
I have this problem on my Joust, but I haven't recapped the monitor yet. My lines start low and as the monitor warms up more (over the course of 10 or 15 minutes) they slowly move up to the top of the picture where they belong. I'm hoping whatever cap needs to warm up just needs to be replaced to keep this weird foldover from happening, but I wonder why yours is still doing it if that's the case.

Do your lines move up at all if you leave it on for a while?
 
I have this problem on my Joust, but I haven't recapped the monitor yet. My lines start low and as the monitor warms up more (over the course of 10 or 15 minutes) they slowly move up to the top of the picture where they belong. I'm hoping whatever cap needs to warm up just needs to be replaced to keep this weird foldover from happening, but I wonder why yours is still doing it if that's the case.

Do your lines move up at all if you leave it on for a while?

Sort of...

There is a smaller line in addition to the lines which appear in the score line, which appears during attract mode. It starts at about 3 inches wide, then slowly decreases in width until it disappears after about 5 minutes.

I'm not discounting caps, but I did recap it only a year ago. There was no noticeable change.

Is there a specific cap or caps which affect this problem? Maybe they were missed or not included in my cap kit.
 
I am not seeing monitor issues...

That looks like a board issue...

Like scratch pad lines... Or a rom degredation defect...
 
I am not seeing monitor issues...

That looks like a board issue...

Like scratch pad lines... Or a rom degredation defect...

Can you elaborate?

I was thinking it was PCB related originally, because it only shows at certain times during game play. I get the "monitor problem" diagnosis, assuming these lines are always there, but usually hidden off the top of the screen. If they're not supposed to be there (or it's not normal for them to be there) at all, then I have to lean toward PCB problem.

When you say "ROM degradation," are you referring to the game ROMs, the video decoders, or something else?
 
I am thinking the decoders or rom. I would verify the roms if you have the ability.

I say this because it has the scratch lines on top before the gameplay artifacts
 
I am thinking the decoders or rom. I would verify the roms if you have the ability.

I say this because it has the scratch lines on top before the gameplay artifacts

Would you (or anyone) know if the Stargate decoder PROMs are the same? I can swap those out to test, if so.
 
1&3

2&3

4&5

4&6

Are paired
Boards shipped with Stargate games had Decoder ROMs 4+5 fitted, however, all later games had Decoder ROMs 4+6 fitted.

Im looking up what robotron uses i think 4&6
 
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1&3

2&3

4&5

4&6

Are paired
Boards shipped with Stargate games had Decoder ROMs 4+5 fitted, however, all later games had Decoder ROMs 4+6 fitted.

Im looking up what robotron uses i think 4&6

Ok. I'm confusing them with the video decoder PROMs on the CPU PCB. I thought that's what you were talking about.

UPDATE: So, if you're correct, I have a full set of Robotron Tie Dye ROMS which I've never installed If the problem is bad ROMs, that should solve the problem, correct?
 
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He is talking about the Decoder PROMs. But I am not sure these PROMs would cause this type of failure in the video. A full screen and longer video would help more in understanding the artifacts.
 
He is talking about the Decoder PROMs. But I am not sure these PROMs would cause this type of failure in the video. A full screen and longer video would help more in understanding the artifacts.

I'll try to shoot a video later, but those lines are the only anomalies. The screen looks very good, otherwise. The only other "issue" is vertical position is in the UP pin position, and the image is still a bit low. The artifacts flicker briefly now and then during normal game play, but the point where I videoed is really the only predictable time you'll see them.
 
Both of my defender cocktails did this same thing. Never bothered me enough to dig into a perfectly working game and possibly make it a non working game.
 
Both of my defender cocktails did this same thing. Never bothered me enough to dig into a perfectly working game and possibly make it a non working game.

It's just one of those nagging things. Mainly, I want to be sure it's not a sign of something more serious. You know; a symptom of pending catastrophic failure or something.
 
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