I have a brother-in-law who asked me to check out his monitor as listed in the subject. What's happening is......nothing.

I've hooked it up to my working second system and all it does is on the front panel, the light toggles between Green and Yellow.
I'm wondering if anyone here has any experience with these. What I've read about them so far shows a tendency to have problems. So, that's not good. It's a nice looking monitor and 'in the day' he paid a handsome sum for it. But, the problem happened after the warranty expired....as usual.
So, if anyone has some insight on these, please let me know.