All the many years I ran tube amps, I did as basically is being suggested.
I always first tuned at low input power to the amp. I often began, with a
new amp, by someone, even if it were my young children reading the meter,
got someone to give me the meter readings to get a feel for presets before
tuning. In some cases, more times than not, I had to even explain to the
person how to read the meter because nothing was digital back in those days.
Once I repeated everything several times, band to band, I marked the front
panel near the tuning knobs with anything, such as strips of clear vinyl
tape we all use for Braille labeling etc. I normally only needed two pieces
of marking tape because all other bands, 80 through 10, were very closely
set to those pieces of tape, that is, to one side or the other. Once
satisfied with all readings, grid current, voltage, and milliamp readings,
in other words, once I knew my settings, I just preset the knobs and band
switch, plugged in a little power, quickly peaked everything with the tone
device I had back then, and dropped the carrier briefly to give the tubes a
rest, although I normally didn't bother once I became familiar with the
presetting of the controls, and then punched it with 100 watts of drive and
found I only had to tweak the settings for a couple of seconds before they
were at maximum. One day, when using my old Heath Kit Warrior amp with 4
811A tubes, quite rugged tubes, of course, I popped all four of the bleeder
resisters across the top of the tube caps. This seemed to occur with that
amp, and those tubes, once every 4 years. Talk about stink. Those
resisters took weeks before the smell in the room finally went away. I had
a friend who used to work for heath kit and was good with amps of all types
but he would bring the new resisters over and solder them back over the tube
caps. He tuned the amp on the air and before he did so, he was very adamant
that they blew because I took way too long to tune up the amp. He had
suggested this a half a dozen times that day and even before he came to
replace the coil resisters. I kept telling him, that wasn't the problem,
but you know how sighted people get some times about such issues. So, Bob
cranks up the amp, driving it with 100 watts output from my Omni D, and
while he was tuning, he caused the tuning condensers to spit, that is, ark.
I said nothing but smiled big time to myself because with that amp, I never
made the tubes spit during tuning because the carrier was never driving the
amp for more than 3 or 4 seconds after presetting the controls. So, Bob has
his good watt meter in line and I asked what the output was because a friend
had pulled out two plug in tube shaped diodes someone had put in for the
built in power supply and wired a circuit board in to the power supply and
it pushed up my voltage, under load, up another 200 volts. He reported
exactly 700 watts output. I said, Ok now Bob, turn everything off, that is,
drop the carrier. Then detune all the controls, even the band switch to
another band, mess up the loading control, the tuning capacitor, and
everything. He did so,. He got up, I sat down, preset everything, snapped
on a full 100 watt carrier without using even low input at first, and was
done in 3 to 4 seconds. Bob said, "I can't believe it. You tuned it way
faster than I did and without arcing it and I can see. I laughed. By the
way, I used 4 811A tubes in that amp for years and replaced them about every
4 years during a period of years when I was super active on CW and I always
ran the amp on CW about 90 percent of the time. The rest was on sideband.
I'd run the 811A tubes down till they would show about 425 watts of output
before replacing them. One time, when I replaced them, I pulled the old
tubes, because they were beginning to ark occasionally, and when I shook the
tubes, I could hear pieces of the plate that had burned off bouncing around
the tubes and yet those 811A tubes still kept working. I've run amps with
572B tubes and the SB220 with a pair of 3 dash 500z tubes and I tuned them
all the same way. I tried buying, from a contest friend, one of his amps
which was the Henry 2K4. During contests, they got 2,000 watts output for
the full 48 hours of the contest on phone or CW. After I had paid him some
money down, a friend called me up with an amp with 3 811A tubes that
Ameritron was making back then and when I saw how small the thing was, I
decided, screw that big amp, my contest and big DX days are long gone so
gave up the big amp for the little one. I know you can push 572B tubes more
and get more output but based on my personal experience, and that of
friends, they don't last as long and they are a little touchier when tuning.
If you really take care of 3 dash 500Z tubes, and I'm talking about
contesting and running thousands of hours of operation time, they will last
10 and 11 years. In all the years I ran the SB220, and I pushed it hard and
always ran it in the highest voltage range even when you weren't supposed to
do that on CW but could do so in side band, and I would run, with 100 watts
of drive out of my Omni, 1200 watts output on 20 meter CW, I never had to
buy new tubes. It's a good thing as much as those dumb 3 500 tubes cost.
So just get a single 8877, rung 5K output all day and all night, and when
the tube eventually goes about 10 years later, it will cost you 1200 to 1600
dollars to replace is all, hahaha.
Phil.
K0NX
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