Turn off the light and look at the neck of the tube, you should be able to see the heater glow. Did you check all the voltages at the CRT socket? You need the right voltages on the cathode, grids and accelerating anodes to get a beam on the screen. Also I would look at the Z blanking circuit that blanks the beam during the retrace between sweeps. You do need to be careful of the HV, but it's not going to shoot a lightning bolt across the room and fry you, just be careful where you poke your fingers.