[Hallicrafters] HT-37 neutralization

[roy.morgan at nist.gov]

Quoting TJRachwal <tjrachwal at comcast.net>:

> Hello,
> 	I have two HT-37 transmitters I'd like to replace the finals in 
> (6146As).  The manual seems a bit complicated to do the 
> neutralization.  Is there an easier way?  Is there some way to 
> monitor the output and adjust C44 without doing all the 
> disconnecting/reconnecting, ...etc.?

Ted,

This same question has come up on the Collins reflector: the answer is yes,
there are simpler methods than our manuals give.

I don't have the details from the Collins community at hand, but basically the
method is:

1) Remove plate AND screen voltage from the finals with all RF circuits intact.
(Applying screen voltage only can damage the screen.)

2) Connect known dummy load and a detector to the transmitter output. The
detector can be a diode rf voltmeter,  or a receiver tuned to the frequency of
interest.

3) Apply grid drive.

4) Adjust neutralization components for minimum signal on the detector.


In the Collins equipment, there is sometimes neturalization applied aroung the
driver stage. One method for dealing with this situation is to have a driver
tube (or tubes) with the one filament pin cut off.  These dummy tubes are used
to set the neturalization.


Roy


Roy Morgan K1LKY
7130 Panorama Dr.
Derwood MD 20855