Re: Microwave oven transformer - tube coil
I'm responding only to the tube-size issue you raised. I will attempt to
describe the tube size in comparison to Brent's 805 triodes.
The 807 is a lot smaller, half as high, and a tetrode (two grids) as I
The others listed there I believe are of similar size but don't really
The 810 is the same physical size as the 805 but can handle twice the
power and (I think) plate voltage [1500 max for the 805; 2500 for the
The 813 is a good, cheap (still) source of a power tube, slightly shorter
than the 805, and a tetrode, but tie the screen grid to the control
The 833 is much larger, about the size of a widemouth Mason jar as I
recall, two big pins out the bottom for the heater, the grid and the
plate out the top..
The 304TL (still available pretty cheap from swapmeets and such), wider
at the top than the 805, you can put 3000 vdc on the plate no sweat,
quite high powered and tough. Takes 10 v 12.5 a to light the heaters
(or 5 v 25 a; not so readily available..
4-250 a; about same size as 304TL, a tetrode same deal as the 813
4-400A slightly bigger; 4-1000A bigger yet, both tetrodes, and quite
3-500Z, similar to 304TL but quite expensive, a triode used in grounded
Hope it helps,