26-10-2016, 10:46 PM
(This post was last modified: 26-10-2016, 10:47 PM by Mike Watterson.)
I built a circuit using a pair of 1j24b Rod Pentodes, based on ECH81 Mixer/Oscillator (adapted to be a modulator), but with six off PP3 (nominal 40V to 56V) for HT
So V1 is the triode section and V2 as pentode instead of hexode.
So the ECH81 version ought to work better
The filaments in series to economically work off 3V (2 x AA cells) at only 11.5mA
Photos uploaded to my server Sun 19 Feb 2012 20:07:24 GMT.
A pair of 1j24b with one wired as triode and the other as Pentode (LO anode V1 DIRECT to g2 V2 with no capacitor!) works in a DK91 / DK92 / DK96 socket as a "heptode" with no change to the battery radio, because the second grid is acting like an anode of a triode. The filament current is 23mA with the filaments in parallel, so for series filaments a parallel "ballast" is needed for 2mA or 27mA. I have two sets that use 1L6, and a DK92 detunes the higher SW bands in the Transoceanic (the other set, a Hallicrafters TW1000 or TW2000 only works on LW, MW and 1st SW anyway). So I must try a the two off 1j24 in it with parallel resistor for additional 27mA.
So V1 is the triode section and V2 as pentode instead of hexode.
So the ECH81 version ought to work better
The filaments in series to economically work off 3V (2 x AA cells) at only 11.5mA
Photos uploaded to my server Sun 19 Feb 2012 20:07:24 GMT.
A pair of 1j24b with one wired as triode and the other as Pentode (LO anode V1 DIRECT to g2 V2 with no capacitor!) works in a DK91 / DK92 / DK96 socket as a "heptode" with no change to the battery radio, because the second grid is acting like an anode of a triode. The filament current is 23mA with the filaments in parallel, so for series filaments a parallel "ballast" is needed for 2mA or 27mA. I have two sets that use 1L6, and a DK92 detunes the higher SW bands in the Transoceanic (the other set, a Hallicrafters TW1000 or TW2000 only works on LW, MW and 1st SW anyway). So I must try a the two off 1j24 in it with parallel resistor for additional 27mA.
