Another New One....

[Old1625]

How about pin voltages on the horizontal output tube....? (Don't measure the plate cap!!! ) That you are getting no whistle indicates that either the output tube is getting no signal from the oscillator, or that the output tube itself is open, or not getting its supply voltage. The screen grid supply voltage could be killed by an open supply resistor, or a shorted bypass capacitor as shown going from screen grid to cathode. If the output tube is getting its required supply voltages, and there is no oscillator drive signal to the control grid the output tube will likely have its plate turn very red. It will kill itself or blow the fuse in short order if that happens.