{Collins} 32S3 Question about Loading / SWR



This is a basic set of issues, probably, and apologies if it sounds
unversed to those who have operated tube equipment for a long time and are
comfortable with it.

I have read the 32S3 Manual, and have searched the CCA reflector archives
for about 2 hours and still have not found the answers - perhaps because I
don't know how to search properly.

That said, here is the problem.  When doing a CW QSO this afternoon on 40m,
using my 32S3 barefoot in combination with my 75S3b (not as a transceiver
but rather driven by its own VFO), the 32S3 would suddenly stop outputting
power; it would just cut out.  That is, on the manual tuner I am using, the
cross needles would go to zero, from time to time, and the guy on the other
end would not hear me.  Then, after a break in sending, I would get power
out again for maybe 20 seconds before the 32S3 went flat again.  The person
with whom I was QSO'ing also told me that when my signal got through, it
had chirp.  (I was reading him at 599, and he the same with me.)

During tuning, I had adjusted my manual tuner during the Tune / Lock Key
tuning procedure so that SWR was around 1.0.  The tuner during this time
was connected to my 80m full wave loop antenna.  During Lock Key, I had
adjusted PA Tuning and the Loading lever to get a grid current of 230mA at
the dip.  I had found it hard to get grid current down to 230mA and where
the Loading lever ended up was right at the 50ohm mark.

I then got off the air, sent an apologetic email, and moved to a slightly
different frequency to try the tuning procedure again.  But first I
exercised the Band switch and the Emission switch slowly, about 10 times
each.  Then, when I went to Tune on the 32S3, I noted that the tuner, with
its same settings as before, was giving me an SWR reading higher than 3.
So during Tune, I adjusted the tuner to get an SWR of 1; it required that I
move the inductor setting 2 taps, and also considerable adjustment on both
capacitors.  I then did the Tune/Lock Key procedures on the 32S3 using
these new tuner settings.  I then found that I could, during Lock Key,
adjust the PA Tuning control and Loading lever to get a grid current down
to around 100mA; the Load lever then was set about 3/8" to the left of the
50 ohm mark.

Using these settings, with grid current at or below 100mA, I found I could
successfully call CQ multiple times, and send series of dits and dahs, and
for a longer period of time than before I lost power in my QSO mentioned
above, without the 32S3 cutting out.  At a grid current of  about 95mA, I
was seeing about 100W on the tuner needle, with SWR less than one.

Questions:

1.  What likely caused the 32S3 to cut out on me?  Is there some protection
circuit that cuts out when the amplifier tubes get too hot or grid current
gets too high, or when the 32S3 sees an SWR that is too high, or if the
amplifier is overloaded in some other way?  Or is the problem more likely
the Band switch and/or the Emission switch, since after I exercised them
the SWR on the tuner changed?  Or something else?

2.  Am I doing things correctly when I do the Tune/Lock Key procedure with
my tuner coupled to my antenna, and not to a dummy load, to give me an SWR
of less than one?  (Manual says on p. 2-1 that tuning into an antenna of
SWR <2:1 is OK, but I fear that if I did Tune/Lock Key procedure with the
tuner in dummy load position, then the 32S3 would see a different SWR when
I went to the actual antenna for actual operation, so that the tank circuit
capacitors in the 32S3 controlled by the Loading lever would then be meshed
too little or too much.)

3.  Am I doing things correctly when I adjust the tuner to get an SWR of 1
while the 32S3 Emission switch is in the Tune position, so that the 32S3
sees 50ohms with an SWR of ~1?  I think Tune puts out only a fraction of
actual power you use on the air, and that Lock Key is closer to what you
use on the air.  Intuition raises to me the question that resonation of the
tank circuit in the 32S3 controlled by the Loading lever is not independent
of the resonation of the tank circuit in the tuner, so that changing output
power might change how the tuner and 32S1 tank circuits resonate and thus
require readjustment of one or both of tuner and 32S3 loading.  So will I
need to retune the tuner and do the equivalent of the Lock Key procedure
when I actually go live on my antenna at 100W?

4.  I have tuned the tuner and the 32S3 for a 7.123MHz CW net tomorrow
a.m., and it does not seem to be cutting out now when I call extended CQ's
for a while.  If I power them down now (both on a variac), will the same
settings work tomorrow morning, or do I need to retune then?

5.  On 40m, how many KHz VFO change before I have to tune the 32S3 again?
And then, do I need to do both Tune and Lock Key?

Thank you, and apologies for any obvious things I should know or should
have learned from my researches.

73,

Jim Ewing
N4TMM
Atlanta, GA



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