Do not disconnect leads leading to the speaker.
If you disconnect the secondary of the output transformer, then very high voltages can be produced which may break down the insulation either in the valve base, in the output transformer or any tone corection capacitor.
If you disconnect the primary of the output transformer, then then the whole of the valve current goes into G3, the screen grid. This will certainly put too much power into it and may melt or distort it.
If you disconnect the secondary of the output transformer, then very high voltages can be produced which may break down the insulation either in the valve base, in the output transformer or any tone corection capacitor.
If you disconnect the primary of the output transformer, then then the whole of the valve current goes into G3, the screen grid. This will certainly put too much power into it and may melt or distort it.