NEC CM-2791 picture shrinks depending on brightness level

wyo

King of Spammers
10 Year Member
Joined
May 22, 2013
Posts
10,433
Trying to figure out what causes this problem. Any ideas?

 

ggallegos1

Cholecystectomy Required.,
10 Year Member
Joined
Oct 1, 2013
Posts
5,168
Could be a cap going bad somewhere in there. Have you been able to open her up and check?
 

wyo

King of Spammers
10 Year Member
Joined
May 22, 2013
Posts
10,433
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

Professional College Dropout
10 Year Member
Joined
Jan 7, 2013
Posts
4,229
Well boys, we will see if this is legit. Just ordered it...Screenshot_20221209_105831_Gmail.jpg
 

SignOfGoob

Butthurt Enthusiast
20 Year Member
Joined
Sep 18, 2003
Posts
2,857
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

Professional College Dropout
10 Year Member
Joined
Jan 7, 2013
Posts
4,229
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.
 
Top