Neutralizing finals.

[Gerald C. Lemay]

For those who might still be interested in how to neutralize a final stage
the old fashioned way, here it is again. The instrument used as a sensitive
RF detector is now an old Boonton  Model 91-AC RF voltmeter at the dummy
load. Used a T connector. Next time, I'm thinking of trying a Tektronix 465B
with a 10X probe. I think the one I have has about 12pf capacitance at the
tip.

1. First turn on the rig and let it warm up for about 1/4 hour.
2. Tune for max power out on 10 meters into a dummy load.
3. Turn off the rig and give it time to bleed the power supply voltages
before the next step!
4. Remove plate and screen voltages from the final stage.
5. Turn on the rig and key the transmitter. Adjust the neutralizing cap for
minimum indication on a sensitive RF indicator (see above).
6. Adjust final TUNE control for max indication.
7. Repeat steps 5 and 6 as needed until no further improvement can be noted.
8. Turn off the rig and wait for the high voltages to bleed off before
reconnecting the plate and screen voltages to the final!!!

Usually, I start on the highest scale of the voltmeter which is the 3 volt
range. By the time I'm done neutralizing, I get approximately 200
millivolts. I think I gave the wrong value earlier. To check if the rig is
properly neutralized, check that maximum power output and final dip occur at
the same point. I've been doing this procedure on most of my rigs which
include Drakes and Heathkits. The only one I didn't use this procedure on
was the Heathkit SB-110A. That one was a special case.

I think one reason manufacturers recommended an alternative method of
neutralization was because it was by far the safest method. High voltages
kill and nobody wants to end up being sued for recommending unsafe methods
or selling in the weasel words of lawyers "unsafe products". As always,
never work on high voltages when tired, keep one hand in your pocket, and
carry a large life insurance policy. This way your wife and kids can live
high off the hog should you accidentally slip and meet face-to-face with
Saint Peter or the Other Guy as the case may be.


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