Tektronix 650
 

This is a very old monitor (1972). If you come across one of these, you should change all the tantalum capacitors first. There are two types of tantalum capacitors. Tantalums that are bad and tantalums that are going bad. Don't try to remove the boards as the plastic clips that hold the boards in, will break. Just work it from the top of the boards.

I've had a few of those over the years and all of them had weak CRT's. Nice find.