30-11-2016, 09:37 AM
(This post was last modified: 30-11-2016, 09:41 AM by Mike Watterson.)
(29-11-2016, 07:06 PM)Sparks Wrote: As I said, I linked it to the cathode, and it threw the readings miles off!
Bob
Double check.
It should only be correct with G2 to HT and G3 to Cathode/OV.
I've tested EF39 "properly" wired as a Pentode.
If you are testing in triode mode (g2 tied to anode), then g3 connection should be cathode or anode depending on valve construction (often Anode, but Rod Pentodes* definitely and Beam Tetrode type Pentodes probably want g3 to 0V/Cathode even in Triode mode).
Hexodes are more complicated.
Heptodes and Octodes: Read data sheets, not short form as the same numbered grid can be HT or 0V depending on design. Example is 1L6 and DK92, looking at pin names they seem incompatible bases, but actually they are different designs, and strangely are actually interchangeable on at least LW/MW (tuning will be badly out on higher frequency short wave bands on many radios).
(* Rod Pentodes are not really Pentodes at all, thus for DF97 pentode, triodised instead of a DC90 triode, you tie g2, g3, anode together, but using 1j24b or 1j29b you tie g2 and anode but g3 goes to f- as it's really a kind of beam device, no real grids at all)
