3-500Z data sheet minutiae

[Opcom]

When things get to the size of a 3-500Z, maybe it is not minutiae, but this apparent discrepancy between the Eimac curves from 1968 and 1980 bothers me from a science perspective. Has this ever been accounted for?

[N2DTS]

Maybe its like the 100TH and 100TL in the old arrl handbooks.
Same voltage, same current (different bias voltages) but one was good for 450 watts out, the other 650 watts out, with less then 650 watts in!

They never corrected it that I know of.
 

[W2VW]

Brett is onto something.

The 3-500Z was originally specified as a 3-400 with another 100 watts plate dissipation. Shortly later the mu was reduced from 200 to 160.

The first ones were indeed zero bias at 2750 or so volts. Later ones require bias which is normally done with a zener around 8 volts.

If one swaps a 3-500 into a 3-400 AMplifier the idle current will be pretty high.

If one swaps a 3-400 into a 3-500 AMplifier the idling current will be really low making the tubes look like they aren't so great.

[W3RSW]

My thoughts too.  So overlay the 3-400 curves on these and see.