Resistance in rectifiying tube

[nee]

Greetings all!

How do I calculate (or is it printed on the data sheet?) the resistance in a GZ34 rectifier?

[FYL]

Resistance *in* the valve? Do you mean plate resistance or minimum source resistance?

Plate resistance is app. 40R for a GZ34/5AR4, minimum source resistance depends on the actual supply and filter type used.

It should be typically at least 150R for a 400V supply and a 60µF cap in a capacitor input filter. Source resistance is the sum of the PT reflected DCR and of any added series R between the PT and valve.

Check for instance page 3, rating chart III in the GE 5AR4 datasheet.
http://www.drtube.com/datasheets/5ar4-ge1959.pdf

[nee]

Resistance *in* the valve? Do you mean plate resistance or minimum source resistance?

I don't know!

I want to calculate how much more voltage would be available using a solid state rectifier rather than a GZ34. My understanding is that the resistance inherent in the tube drops some voltage, whereas the SSR does not.

[FYL]

I want to calculate how much more voltage would be available using a solid state rectifier rather than a GZ34. My understanding is that the resistance inherent in the tube drops some voltage, whereas the SSR does not.

OK, then it's plate resistance. A GZ34/5AR4 will typically drop peanuts to 40V depending on current thru it (remember Ohm's law?) - you can expect 16V at 200 mA, 20V @ 300 mA, etc., a standard silicon diode will drop app. 0.7V.

[tubeswell]

The rule of thumb for voltage dropped from different rectifiers (which is 'close enough') is:

SS - 1.4142 x the HT VAC
5AR4 - 1.31 x the HT VAC
5U4G - 1.21 x the HT VAC
5Y3G - 1.11 x the HT VAC

See also the attached rectifier voltage chart courtesy of Billy Penn.

[nee]

Thanks all. Incredibly useful information.