My set had Been working fine. Recently I have not been able to get the kine to light until I turn the brighness almost all the way to the right. I can only get a blue screen with some light lines. Do uou have any idea what the problem could be?

Does the sound still work?

Sound works fine

Can you measure the voltages at the heater, grids, cathodes, and screen grids (if you have a meter that can measure that high). Those may give us some insight into the problem. Also if you have an HV probe please measure and report the HV, focus, and convergence voltages.
Also in opperation there is no purple or blue glow in the neck of the CRT correct? If the CRT is going gassy and there is enough gas for abnormal conduction between elements in the neck, but not enough to extinguish the beam or cause neck to HV arc then that could possibly cause symptoms like this as well.

These readings should tell us what is causing the brightness to be lower than what it used to be.

For loss of video see my post in the other thread on this set that you and I replied to.

Have you checked the 6BC7 dc restorer?

If the raster is dim and maintaining focus, this would imply the crt is being biased off.

Is this the set you had listed for $6K and then you ended the sale early??? I thought you said you were out of the country? And couldn't answer questions. .. just wondering. .