07-10-2023, 06:03 PM
MrFixr55 Wrote:The values for primary impedance I got from my docs are higher than those quoted by Dale and Ron, but go with them. My info was from the RCA Receiving Tube Manual, but possibly at a different voltage.
Which edition? In the 650 the 42s are triode-connected in a push-pull amp, and the load impedance also depends upon bias - in the 650 they have fixed bias. See RC-13 p. 129. It is the only RC edition with full characteristics for the 42. RC-11 and RC-12 have only partial characteristics. From RC-14 on you have to look at the 6F6, which has the same electrical characteristics as the 42 and the 2A5.
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/