Light on the screen is progress. You have HV of some sort and the vertical sweep circuit is trying to work.
Don't play it for long periods with a bright horizontal line on the screen. That can eventually burn a permanent dark line in the picture tube.
If somebody else messed with it in the past, that is all the more reason to sit down with the schematic next to the TV and double-check
everything for wiring mistakes, components with wrong values, dripped blobs of solder, short circuits caused by accidentally pushing the wire of a component so that it touches something else, etc., etc.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html