NEC CM-2791 picture shrinks depending on brightness level

wyo

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Trying to figure out what causes this problem. Any ideas?

 

ggallegos1

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Could be a cap going bad somewhere in there. Have you been able to open her up and check?
 

wyo

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Could be a cap going bad somewhere in there. Have you been able to open her up and check?

Yeah, there's nothing obvious. Full recap would be a lot of work. There's virtually no info on this model so unsure where to start.
 

skate323k137

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Well boys, we will see if this is legit. Just ordered it...Screenshot_20221209_105831_Gmail.jpg
 

SignOfGoob

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The technical term for this is “bloom”, I think. All TVs used to do it a little until the Wega era. This is obviously out of control.

Caps are almost certainly the issue. Maybe you can concentrate on the areas of the input stage and the adjustment circuitry.
 

skate323k137

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This is a mad old thread but I hope the manual I found is legit. Only like half a dozen people have even posted about these exact monitors over the years. I had two and sold 1 to @3rdStrikeMike years ago. The one I kept I use for light gun games but I want to try the digital CGA mode with a Laser 128 (Apple IIc clone) and there is -no- documentation on this monitor online.
 
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