Quote:
Originally Posted by old_tv_nut
Ok, here are the plate characteristics with the load line. You can see that most of the tube's capability at higher plate voltage is wasted.
Transconductance varies around 4000 to 7000 micromhos; call it 5000. Then the output for 3 volt input can vary from 30 to 72 volts p-p depending on the contrast setting.
Linear approximation:
Cathode current swings 5 ma per volt Vg-k.
For 1 v Vg-k swing, 33 ohm cathode resistor swings 5x.033 = .165 V; for 3v input, V g-k swing is 3x1/1.165 = 2.575; 2.575x5x5.6=72.
For 1 v Vg-k swing, 363 ohm cathode resistor swings 5x.363 = 1.815 v; for 3v input, Vg-k swings 3x1/2.815 = 1.07; 1.07x5x5.6 = 29.8
Could it be as low as 16 vpp at minimum? Probably.
Edit: fixed a couple of typos above.
Note: In circuits lab I PO'd the TA when I asked how much the tube characteristics could vary and he obviously had no more idea than I did. (We later became good friends and colleagues when I went to work at Zenith.)
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Thanks for doing all this. I suppose it is not a big surprise that the tube is not used to its full potential in a transformerless TV with such low B+. Out of curiosity, during what time period did you work at Zenith?