First post, by Rita's Cafe
This 15" NEC VGA CRT monitor has recently started exhibiting some strange issues with the picture. Sometimes the green channel is absent other times it appears that the blue and green are absent. More commonly all channels are present but the picture appears dark on the top and bottom halves of the screen with a small horizontal area in the middle that is still bright. See attached photographs for a better explanation.
The issue presents itself after a period of operation. Sometimes this can take two hours to show up. Other times it will happen within five minutes of use from a cold start.
The attached photographs show test patterns in 640x480 and 800x600. Interestingly running “edit.com” in DOS shows the issue but the command prompt appears fine.
All photographs are of DOS applications. The same issues have occurred using a different motherboard and two other GPUs.
Information about the monitor:
NEC Multisync XV15
The RGB amplifier is an LM1203.
Purchased three months ago and worked flawlessly for the first two months.
Hopefully somebody here will recognize these symptoms and be able to point me in the right direction. What is causing this and how do I fix it?