Edmund H. Ramm wrote:

Lots of "ifs": If the mode switch shown in the diagram only has
the three positions AM - VFO Beat - CW, and if the switch's position
shown in the diagram is the AM position, then there is no protective
bias in AM mode, indeed.

ok, that's what it seems to me too (the circuit drawing isn't also very
easy to follow sometimes), and that's what I can measure on the real
thing.


Do you know this urge to wring the designer's neck until he discloses
what drugs he was on when he designed this circuit?

Other transmitters use at least a kind of brute force circuit to pull
down the PA valve's screen grid voltage with no exitation present, in
order to keep the anode dissipation low enough.

I agree, if you don't monitor the G1 current in AM mode, the 6146 will
not survive for long time.

By the way, I ordered a new 6146, the PA has no neutralization circuit so
probably even the 6146B would work fine, but none of my used 6146B is in a
known state, so I would just add other unknowns if I'd try with them.

73
Frank IZ8DWF