Why does the camera...

[old_tv_nut]

Tripod
May need manual focus, try auto vs. manual.
Manual shutter setting 1/30 second or slower to reduce/eliminate shutter bar;
Manual aperture, or exposure compensation (+/- lighten/darken) because the meter gets fooled by the difference between the usually brighter picture and the darker surround;
Generally, set white balance for "shade," but you will still probably need to adjust in post processing, especially for 50's and later monochrome (very bluish phosphor) and vintage color sets (very cyan "9300K + 23MPCD" white balance, essentially not enough red).

Getting a good shot of both the picture on the screen and the cabinet is very tricky. Professional photographers for the TV manufacturers would make two images, one for the picture and the other for the cabinet, and cut/paste them together (that was in the very few cases where the ad read "actual TV picture"). Most ad pictures did not use a real off-screen picture, and when rules were instituted, had to say "simulated picture" in the fine print.