[AMRadio] 6146A's Arrived (was DX-100B on Phone - bad audio distortion/ oscillation)

Peter G Petropoulos peterp at ouzo.njit.edu
Wed Dec 7 18:47:05 EST 2011

On Wed, 7 Dec 2011, John Lyles wrote:

> The DX100 can indeed be neutralized, using the gimmick wire probe
> technique as used in other Heathkit transmitters.

the pi-network interstage coupling loads the PA grid and does not require
neutralization (see, for example, pg. 160, arrl 1957 handbook, lower
right paragraph on grid loading).

In any case, it won't hurt to check the 47 pF capacitor that goes
from the 6146 grids to ground (the "loading" cap of the grid pi-network
between the 5763 and the 6146s).

Finally, if it is decided that the problem is related to
neutralization  then some experimentation with the value of that cap
may be in order (increase it) instead of adding gimmick wires. The
handbooks say that that cap should be of the order of 100 pF.


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