Hi, You may find you can improve the picture by overrunning the tube heaters a bit. It may shorten the time it takes for the picture to improve at least.
If you identify the heater connections and run them from an ext transformer, you can see how much boost it needs before modifying the heater supply in the set.
Does the set have a resistor in series with the heaters? If so you could try lowering its value or shorting it out; it has worked for me on other makes.
best of luck! Richard.
