Wells 2774 vertical roll

Chevyjim

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I have a wells 2774 monitor that I can't adjust the vertical hold. I can get it close to sometime lock in for a second, but it starts rolling again slowly. Could this be cap issue, or an IC? I have changed the control board and it does the same thing. Any help would be appreciated!

Thanks,

Jim
 
Let me clarify, the monitor frame has WGM2774, but it's actually a K7401 chassis. Sorry!

Jim
 
Let me clarify, the monitor frame has WGM2774, but it's actually a K7401 chassis. Sorry!

Jim


Yeah, the 2774 indicates that it is a 27" 7400 series chassis. The lack of lock in could be a cap problem or it could be a failing vertical hold pot. I don't think there is a specific service bulletin for not locking in, so general troubleshooting rules apply. I'd cap the chassis, checking for cold solder joints and then reinstall and see what I have.
 
What game are you using it with?

Not intended for any specific game yet. It's just one of a batch of monitors someone gave me that need attention. I'm using a GME MT830 video pattern generator for testing. Think I'll throw some caps in the vertical circuit and see what that does.
 
Well, the reason I asked was to determine what signal you were sending to it. I assume you know not to connect the vertical sync if using composite negative sync?
 
Well, the reason I asked was to determine what signal you were sending to it. I assume you know not to connect the vertical sync if using composite negative sync?

OP: this entirely sounds like your problem

I would know... I just did it on a Pac-Man last week.
 
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