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The "gassy" sound you were hearing was likely high voltage arcing and leakage. It is a "hsssssss" that may sound like gas leaking from a crack in a pipe or cylinder. If the HV leakage is severe enough it will keep any image from forming on the screen at all. As the leakage diminishes then whatever image can show will show on the screen. Perhaps the warming of the set has driven out the moisture that enabled such discharge to occur.
As for the gray raster with no snow you may want to examine the sound output tube--believe it or not. A lot of these old sets used the sound output tube as a series voltage regulator, where all the picture IF stages and the tuner would feed off a 130 volt supply right off the cathode of the sound output tube. If the tube is flashing over then it is possible that it is weak or altogether bad, or that the electrolytic capacitor on the 130 volt line is shorted or severely leaky. Either way the result is that there is low or no 130 B+ supply to the tuner or the picture IF stages. Sometimes with this problem one can turn the volume control way down, and then turn it up rapidly, and the raster will suddenly brighten and produce snow for a brief moment. The output tube can be weak enough to supply insufficient B+, but still have enough life to produce sound.
(Edit) Reading your last posting where you get sound but no picture at all leads me to want to re-examine the video amp stages.
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09-27-2008, 08:31 AM
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