The AM Forum

I have 'found' a box of maybe 175 6J6's. All are "w" or equivalent type in individual cartons that are unremarkable except Labeled as a replacement part for for Sperry Gyroscope, so they seem to be the 'good' kind if there is such a thing. All seem new. I tested two on the Hickock and both were like new.

So, what can I build with a few of these? Anyone done anything remarkable with a 6J6?

Someone also gave me a chest of resistors today. Many large ones. The chest is about 30x30x48" and is too heavy to lift.

So it has been a good day for junque.

6J6 makes a great oscillator - use 1 section as the oscillator, use a RF choke on the cathode to cathode couple to the second section, and ground the grid thru a grid leak resistor so the 2nd section acts as a buffer.

They are desgined for push-pull service (the pinout makes this easy) and will do a bouple watts in Class C IIRC.  They make a decent audio amp (you just have to be wary of that common cathode though).

I think they were used in a DC amplifier bridge circuit for driving a meter across the plates.  We used similar in Birdwell's Brown amplifiers. Been a long time ago.

They're good for quite a high freq. so might have been used in FM multiplex drivers to send signal (2 or 3 watts) from bottom of hole to uphole electronics in service truck.  Just can't remember.

Anyway quite a neat low power xmitter could be built with about 6 watts out using a pair in ("quad") push-pull.  Same for the modulator. Medium mu so you'd probably want a carbon mike if you stick with all 6J6's.

They make great PULLEN Mixers which like the common cathode anyway. One section is the mixer and the other is the injection buffer with the injection via the common cathode.

Mike WU2D

The Pullen schematic there just reminded me of a differential input stage. I found the curves for the 6J6. I don't know why it was never shown in the "resistance-coupled amplifier" sections of the manuals, it is nice and linear.