I don't know what the 3-500Z's like to look into for a load but it sounds perfectly feasible to me.
John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Jankowiak Sent: Thursday, December 09, 2004 8:39 PM To: [email protected] Subject: [AMRadio] 3-500Z vs 4-400A Ok, in the name of versatility, suppose there's this simple transformer coupled push pull modulator chassis, set up for 4-400A's in class B. (yes but read on) In the chassis, the socket terminals which would go to the 4-400 control grids have a 20K resistor between them and the screen grid terminals. The idea is to limit the control grid current of the 4-400, and let most of the audio drive the screen grids. Kind of like the old 120W class B zero bias 807 modulator from the ARRL and RSGB handbooks. I won't nit pick about exactly what class it is, probably more like real-world AB2. Ok. so I drop in a pair of 3-500Z's. Of course the 20K resistors would not matter when the 3-500Z was inserted, as all 3 non-filament pins are connected to the triode's grid. I throw a DPDT switch, to change taps on the driver transformer from ones supplying 1000V peak grid to grid (to drive the screens of the 4-400's as triodes), to those taps supplying a lesser voltage appropriate for the 3-500Z's. workable? Interesting? nuts? Best regards, Patrick
