Magnavox CT 220 Anode Voltage.

[JohnCT]

Sounds a bit low, but it shouldn't drop that much with brightness change unless the tube is being over driven. If the HV drops by half from dark screen to normal picture brightness something is definitely not right.

If the picture "blooms" when you raise the brightness, that normally points to a bad HV rectifier tube or HV caps around the fly. If the picture shrinks when you raise the brightness, it's more likely a bad horiz out or damper.

John