Samsung 750s approx 5 yrs old, text is ok but video and jpg's are too dark.
There are two adjusting 'screws' on the transformer but BOTH are for focus.
The only other adjusting screws I can find are on the neck marked Yv Yh Yhc.

Here is a pic of the 2 adjusting screws on the transformer. The one on top
cannot be turned.

http://www3.telus.net/shared/Monx.jpg