The Tune variable roller inductor (unique to certain Henry amps) pickup, as I
have stated in previous posts, had a loose connection to the coil at the sweet
spots for my most used bands of 80 and 40 meters. When tuning the amp, a
frying sound would occur right at plate current dip and meters would be
somewhat erratic when this occurred. I temporarily solved this over a year ago
by applying some conductive grease to the roller and attempting to tighten the
pick up. The fault redeveloped but this time also brought an arc between the
front most fixed cap for plate "C" to ground. The arc would go from the high
voltage top of this cap to a small angle bracket that holds that part of the
band switch together, scarring the material the band switch is made of and
cracking the door knob cap. This material has a name but I cannot recall it
now, it looks like black fibered material.
As I later discovered the arc was due to excessive RF build up in the tank
circuit that was not able to go out of the amp to the antenna. It found the
weakest point in the tank circuit and made an escape.
When I learned Henry would no longer make HF amplifiers such as the 2K Classic
X or any other high power tube amplifiers, I decided to contact them and order
a new roller inductor and band switch assembly.
I eventually disassembled the RF deck from the floor console stand and removed
the original roller. I discovered this was no easy task but persistence and
patience prevailed and with the assistance of multiple digital photos the new
roller was fitted in the original's place.
All areas of the amp were next cleaned with compressed air, dusted with paint
brush and wiped with dry toweling to remove the dust build up.
Due to work schedule, and other time considerations, the reassembly did not
occur until yesterday. I am glad I made the photos for reference.
Final results, with a new pair of 3-500zg's I loaded the amp in CW setting and
realized 1200 watts on 80 and 40 into the dummy load and the anticipated
sizzles, bangs, or pops did not occur. Instead, the amp made power steadily
into the dummy load and only the lower portion of the tubes began to turn a bit
of color. Voltage dropped from 3000 to 2800 volts under load and current was
running .700 which indicates approximately a 61% efficiency.
I loaded each band on up in frequency and had slightly less power on 10 meters.
Next I began holding SSB qso's on the various bands, 10 and 15 were call CQ
only with no contacts. 20 meters was open and several qso's were conducted,
similarly with 40 meters. All reports indicated excellent audio and there was
no erratic behavior from the amplifier during this afternoon long campaign.
The cabinet remained only slightly warm to touch throughout.
I am pleased with the repairs and plan on giving the amp another 10 plus years
of service, probably continue annual cleaning and inspections, unless something
further problematic develops.
Best 73's
Gene Bigham KB0GU
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