Color separation

Sememmon

Crazed MVS Addict
Joined
Jun 14, 2005
Posts
145
I've got a rev1 mvs-4-25 that I think has the original monitor installed. I'm not positive on that, but given the shape of the cabinet when I received it, I'm pretty sure it was all original. One of these days, I'll have to get around to the back and check. Anywho, I've noticed over the years that in the top-left corner, I've got a small amount of color separation. For example, on the white cross hatch, I can see separate lines of color for the very top-left-most corner. It is most noticeable on text.. and I can easily see the blue separating from the rest.

What causes that? Is it fixable? If so, how?

Thanks for the info/help!

Edit: It looks to be a Zenith tube in a WG K7000 (or compatible) chassis. Either this (same ICs) or this (Zenith-made K7000?).

Edit: Here's an example of the separation:
Spoiler:
IMG_20190606_221618.png
 
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Opel

Bashful Neophyte
Joined
Oct 28, 2001
Posts
16
I'd recommend getting fresh capacitors on the chassis and neck boards, as well as new transistors on the neck board, and see how that looks for you.
 

Sememmon

Crazed MVS Addict
Joined
Jun 14, 2005
Posts
145
Thank you for the suggestion! Since posting the original message here, I got a thread going over at arcadecontrols.com as well .. and got a cap kit installed. Unfortunately, I broke something along the way, causing me to lose vertical deflection. I sent it off for repair last week. Will tackle this again once I get the board back and will post the results here.
 

DaisyAge

Galford's Armourer
Joined
Jun 10, 2018
Posts
453
Use a convergence test screen to help you out. On the yoke there are rings for each of the red green and blue guns. When you have separation that usually is an indicator that the convergence is out of spec. Otherwise you possibly have a strong magnet near that corner causing some issues? I strongly recommend watching multiple videos on adjust convergence before trying it yourself, good luck!
 
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Sememmon

Crazed MVS Addict
Joined
Jun 14, 2005
Posts
145
Thanks for the tips on the rings! I've always wondered how they worked. lilshawn over on the arcadecontrols.com forums told me a bit about those, too. Wouldn't adjusting those affect the entire screen though and not just the top-left corner?

The guy servicing my chassis pcb mentioned convergence strips/pads .. and possibly gently adjusting the cone to see if that makes an obvious difference.

I will do some searching for convergence videos, as you suggested. If there is a specific one you have in mind, please do let me know.
 

DaisyAge

Galford's Armourer
Joined
Jun 10, 2018
Posts
453
Yes usually adjusting convergence affects the whole screen which is why I was wondering if there was a magnet or something else affecting that corner. You could also try degaussing your screen because that you fix it as well but if the monitors inter deguass isn't working you'll have to buy a wand. Never heard of convergence strips but if that's a thing I'd try that out first. Iirc I only recall magnets being put on to help with geometry but I don't do a ton of monitor repairs either. This might help: https://www.youtube.com/watch?v=xAbqucrWHjU
Edit: Upon inspecting your picture I definitely think this is the right approach, it looks like your screen has been pulled off into that corner too far. Adjusting the ribbon magnet on the backside should fix this.
 
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