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Utah Jr. Transmitter Restoration
From the engineering
diagram, it appears that Utah first offered this unit for sale in late
1937.
Aimed the new ham, it was a entry level unit, sold for $15.95, and
offered CW only operation.
The design is quite simple, consisting of only one rectifier tube, and a
single 6L6. Despite the simple
tube layout, Utah claims coverage from 160 to 10 meters with the
appropriate crystal and coil.
Overall, I found my unit quite clean, but upon disassembly on my
workbench to replace the
missing line cord, I discovered that the some
had replaced the power transformer.
Further testing revealed that the
electrolytic filter capacitor was shorted, most likely the
reason the
original transformer needed replacement. The original filter cap was
encapsulated
in wax, inside a cardboard carton, so a suitable
replacement will need to be fabricated.
I believe that I can melt the
wax out with a heat gun, and install a modern electrolytic capacitor,
while still retaining the vintage look. Clearly someone had been working
on this unit before,
little wiring was connected in the power supply, it
appeared that someone had started the project,
but not finished. I removed all components from the power supply deck,
and will rebuild from scratch.
The RF deck was another story, complete, but very much in need of a good
cleaning. In addition, the
kit builder was not terribly skilled, and most of the soldering needed
rework. These kits were sold as an
entry level kit, often to newly minted hams, so one would expect that
experience in kit building would be
lacking. I have no doubt that the unit worked at one time, but had
clearly been sidelined with the power
supply failure. As pretty as much of this vintage gear is, I like it to
be functional, and not just for shelf ornamentation.
So restoration needs to be carried out in a manner which is both authentic, and
yet allows consistent
and reliable operation. Whenever possible I always use new old stock parts, and
this kit will be rebuilt in my usual manner.
Following the same strategy of the power supply deck, I disordered and
removed all components from the RF deck,
inventorying all in Ziploc bags
to ease the future rebuild. The resistors, caps and chokes will be
checked, but much
of the cloth covered vintage wiring is showing its
age, and will be replaced.
With the deck components removed, but leaving the air variable caps in
place, I then ran both the RF and
power supply decks through my
dishwasher, placing them on the upper rack to avoid heat damage.
This
treatment, really does wonders, and no damage occurs if the system is
run on low heat.
I would however, suggest removal of any component which
has a decal or label.
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| Front of my unit |
RF deck is upper, Power Supply lower deck |
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| Close up of power supply |
Close up of RF deck |
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| Power supply removed from chassis |
Bottom of supply, note disconnected wiring |
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| Top of RF deck prior to cleaning |
After a trip through the dishwasher! |
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| Bottom of RF deck, needs some rework |
Overall view of bottom of RF deck |
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| Air variable cap on RF deck, xtal to the
right |
Output loading cap on RF deck, Cardwell type |
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February 20, 2008 - Back From The Powder Coaters
April 2008 - Reassembly Work
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Amateur Radio Station W1UJR
