Restoring The 1937 Utah Jr. Transmitter - Completed January 2009

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Background
Utah Radio Products from Chicago, IL is perhaps better remembered today for its transformer products rather than for its radio kits. Yet, like many of the other transformer manufacturers of the day, Stancor, Thordarson and UTC come right to mind, Utah offered a number of transmitter kits, beginning with simple two tube table top units and carrying up market to high power floor rack models.

The radio kit concept was shrewd; many hams, burdened with budget and time constraints, or the lack of tooling and technical skills, could not scratch build their own gear. Utah realized that it was a simple matter to offer a kit, complete with the pre-punched and drilled sheet metal, that the average ham could assemble with minimal hand tools. Aside from the profit realized selling the kits, this familiarized the ham of the day with the offerings of the company, and quite possibly led to future component sales.

Unfortunately many of these transmitters are lost to us today, as is much of the early radio gear from the 1930s. It has fallen victim to parts cannibalization, component failures, wartime needs or has simply been discarded when thought to be antiquated by newer technology. Still, there is great joy to be found in discovering, restoring, and operating one of these icons from our radio past, and much to commend the folks that take the time to get these artifacts on the air.

From the schematic diagram, and supported by Raymond Moore’s excellent book “Transmitters - Exciters and Power Amplifiers”, it appears that Utah first offered the Utah Jr. for sale in late 1937 and that production of the kit ended in 1939.

Aimed at the new ham, this was an entry level kit which sold for $15.95, not cheap, but certainly affordable for the day. Aside from the transformer, Utah appears to have sourced most of the other components from standard manufacturers of the era. The two air variable capacitors came from Cardwell, the plate meter Triplet, the switches and keying jack appear to be Switchcraft.

The Utah Jr. tube complement was rather simple, consisting of only one 5Z4 rectifier and a single 6L6 tube, providing a RF power input stated to be 25 watts. No modulator was included or offered, so the Utah Jr. is strictly a CW only rig. Despite the rather simple circuit design, Moore's book claims band coverage from 160 to 10 meters with the appropriate crystal and coil sets.

You can click on the link below to view the Utah Jr. manual in Adobe pdf format, courtesy of John K2TQN --> Utah Jr. Manual.

Found Condition
Overall, I found my unit to be in good condition for a transmitter now approaching its 75th anniversary. The exterior black wrinkle finish on the cabinet was in very good condition, needing only a thorough cleaning. I find that a lanolin based hand cleaner, like D&L or GoJoe, works very nicely in cleaning the decades of grime from the paint, but always test a small and inconspicuous area first. A light spray of Wurth "Cockpit Cleaner" works wonderfully to bring back the luster to the finish.

Although the cabinet was a in good order, the chassis of the RF and power supply decks were another matter. Both were showing signs of rust forming under the paint, and in several spots moderate rust pitting of the metal was observed. I therefore planned to strip down and refinish both of the sheet metal chassis, either with paint or a powder coating process. I also noted the power cord was missing, but had seen that often in the past, when a well intentioned owner had cut off the cord due to deteriorated insulation or an internal problem with the unit.

I began the restoration project by removing the power supply deck from the cabinet for inspection. Upon disassembly on my workbench to replace the missing line cord, I discovered that someone had replaced the original Utah power transformer with a Stancor unit, but had failed to wire in the leads. Fortunately the original Stancor specification label was still on the end bell covers, allowing me to easily reference the transformer voltages and current rating.

Further testing revealed that the electrolytic filter capacitor was internally shorted, most likely the reason the original transformer needed replacement. The original filter cap was encapsulated in wax within a cardboard carton, so a suitable replacement would need to be fabricated. Clearly someone had been working on this unit before as much of the wiring was disconnected in the power supply. It appeared that someone had started the transformer replacement project, but for some reason had not finished. I removed all components from the power supply deck for testing and inspection, and as most of the wire insulation was quite brittle, I planned to rewire the power supply from scratch.

The RF deck was another story, quite complete, but very much in need of a good cleaning. In addition, it was quite apparent that the kit builder was not well skilled, and most of the soldering required rework. As these kits were sold as an entry level transmitter, often to newly minted hams, one would expect, and often finds, that lead dress, assembly and soldering are not quite up to commercial standards. With that said, 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 also be functional, and not used just for shelf ornamentation. So the restoration needs to be carried out in a manner that is both authentic, and yet allows consistent and reliable operation. Whenever possible I always use new old stock parts, and this kit was rebuilt in my usual manner. I've written a bit on my philosophy on restorations, you can view my thoughts and past restoration work at --> Past Restorations.

Disassembly
Prior to any disassembly, I always photograph both the chassis and wiring. This is where a digital camera shines, for it allows one to take multiple photographs from nearly every angle. Not only is this process good for the requisite “before and after” photos, but it serves as a very handy guide during reassembly. While this may sound redundant in cases where schematics are available, the photos show lead dress and layout in a manner that is nearly impossible to convey with just a schematic.

My standard process for cleaning a small chassis, especially if heavily soiled, is to use Simple Green and a shop rag to wipe down the deck. Next, I turn the deck on its side and spray a heavy coating of cleaner on the top and underside. Once this is allowed to work its magic for perhaps 5-10 minutes, I then rinse clean with tap water. A quick trip into a 200-degree oven for 5-10 minutes does wonders for the final dry cycle. I then use a Q-tip to remove any residual staining or dirt, especially around the terminal block, tube sockets, or other hard to reach areas. Once the chassis is air-dried overnight it is ready for reassembly.
 
Following the same strategy of the power supply deck, I disassembled and removed the components from the RF deck, inventorying all into Ziploc bags to ease the future rebuild. The resistors, caps and chokes were checked, but much of the cloth covered vintage wiring was showing its age. I discarded most of the wire, saving only the inter-chassis wiring harness as a template for fabricating the replacement.

Most air variables, because of the multiple individual plates, are very difficult to properly clean without damage, and as any dirt here provides an easy arc over path, it is well worth the time to thoroughly clean the capacitor plates and hardware, and a dishwasher makes quick work of this task.

With the RF 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 at low temperature. I would however, suggest removal of any component that has a decal or label. The units emerged looking like new, and I took a few moments to clean and tighten all hardware, and then properly lubricate the shafts on the air variable caps.

With the chassis now stripped, I sent both off to the powder coater with instructions to remove the old paint, and refinish in a low gloss black to match the original color. Powder coating is a modern, and quite durable method to finish sheet metal. During the powder coating process, the sheet metal is electrostatically charged so the aerosol powdered paint will adhere to it, and is then baked at high temperatures. The result is a most resilient finish, and a close match to the old black flat or wrinkle finishes. Any areas, for example ground lug mountings, which should not be to be powder coated, can be masked off with a special high temperature tape. After a week at the powder coating shop, both chassis were returned to me looking like new. The rust was gone and the finish looked very much like a vintage paint product.

Putting It All Back Together
With the chassis now freshly refinished, the task at hand was reassembling the unit. In many ways it was much like assembling a kit, with the parts labeled and placed in Ziploc bags, and the digital photos of the original wiring layout serving as a schematic.

The first task was the rebuilding of the power supply deck, and properly wiring in the replacement power transformer. Thankfully, whoever had chosen the transformer so many years ago had chosen well. It fit right in place on the deck using the original mounting holes. All I needed to do was to bolt it to the chassis and then extend the leads, which in the past had been unfortunately shortened.

The next step was the restoration or replacement of the shorted filter capacitor. I mentioned earlier that this capacitor was enclosed inside a cardboard housing, and sealed with wax. A modern solid state replacement would simply not look right here, so I decided to instead rebuild the original capacitor. The biggest challenge was melting out the wax, and removing the shorted capacitor from the fragile cardboard housing.

I had considered melting the wax out with a heat gun and installing a modern electrolytic capacitor. Concerned about the use of heat on the now brittle cardboard housing, I opted for a different method than the heat gun, instead using a microwave oven. A few minutes in the microwave was all it took to soften up the wax, allowing easy removal of the failed capacitor, and the installation of a modern day replacement. I then melted the removed wax, and poured it back into the cardboard case, making the repaired unit look like a 1930 vintage replacement.

As the original cloth wire had greatly deteriorated, and I wanted to make the little Utah last another 70 years, I replaced all the wiring in the unit. I used cloth covered push-back wire, color coded to match the appropriate voltage source, green for the filament leads, red for B plus, etc. One concession I did make to the modern world was the use of heat shrink tubing on the chassis wiring ends, for the sake of keeping the cloth covering from unraveling. I consoled myself thinking that it looked much like the “spaghetti” tubing of the 1930s. With the power supply assembled, I tested the various voltage outputs on the bench. Satisfied that all was working well, it was time to move on to the RF deck.

The assembly of the RF deck took just a little more time than the power supply, lead dress being important here, but the process was quite straightforward and a few evenings work brought me a fully assembled RF deck, ready for testing. A careful inspection was made of the 75 meter plug in coil, and the Arcturus 6L6 power tube was also checked. The air variable capacitors, fresh from their trip through the dishwasher, gleamed like they were new. I did replace some of the more corroded and discolored hardware with stainless fasteners, and cleaned the powder coating from the few chassis holes where a ground connection was critical.

The last step remaining was one of the more intimidating to me, for I had never really laced up a wiring harness before. I had repaired lacing in the past, but this time I needed to completely lace the replacement harness that I had fabricated. After three or four aborted attempts, I finally succeeded in producing a lacing style much akin to the design used by the original builder. If you need wire lacing instructions, and there are several different methods, like there several ways to tie your shoe laces, check the early ARRL handbooks from the 1930-40s. I used lacing cord graciously supplied by W2DGB a few projects back to lace up the harness and to secure the wire layout at the terminal strip.

Live To Air
What can I say about the testing process other than the unit worked the first time it was fired up. With the installation of the proper 75 meter crystal and the connection of my light bulb dummy load, we were in business. Careful loading and tuning brought the plate current up to the Utah suggested 80 ma, and the little 25 watt light bulb glowed brightly.

I used my 1940s vintage National HRO as a test receiver to listen to the note when the Utah Jr. was keyed. I found the note pleasant, with a very slight amount of chirp, somewhat lessened by lightening the loading of the output network. As this is a link coupled rig, it prefers a high impedance antenna connection, ideally into a balanced antenna. I did find, on the suggestion of Larry NE1S, that I could use an external air variable in the antenna line to “tune” the impedance to better match the Utah Jr’s. narrow loading range.

While the Jr. transmitter was one of the more humble of Utah’s offerings, it is a very robust, simple and quite solid transmitter. Paired with a contemporary receiver of the day, say the venerable National HRO or FB-7 series, it would represent a very respectable station for the radio newcomer, or ham on a budget.

Today, the recreation and operation of such a vintage station is a joy, as one is occupied not just with the logging of call signs, but also with loading and tuning, transmit and receive switching, and zero beating, all of which are activities we miss out on with today’s solid state transceivers.

Indeed, that is perhaps the very thing that is most enjoyable with vintage gear like the Utah Jr., the tactile operation, the tangible feeling of really operating, not just listening. The gentle hum from the power transformer, a smell of dust burning off as the vacuum tubes heat up, the warm glow of tube filaments, the solid “clank” of the T/R relay pulling down, the little warble or musical note to the CW signal, and the dance of the plate meter needle while sending. When most of today’s QSOs are completed with the ease of a cellular phone call, it is station like the Utah Jr. and National FB-7 that remind us of the real magic in radio; that radio, real radio, is not just about listening, but about smell, touch and sight.

More Information
John Dilks K2TQN, the author of the wonderful vintage radio column published each month in QST, wrote an interesting piece about the Utah Jr. in the March 2007 issue. John has some additional information and photos of the Utah Jr., as well as an archive of his other articles, on his website which can be found at -->> K2TQN website.

Raymond S. Moore’s excellent reference, “Transmitters - Exciters and Power Amplifiers”, mentioned earlier, is another resource for information on the Utah and other vintage transmitters. Covering a span from 1930 to 1980, Moore has compiled a wealth of data as to production dates, tube complement, selling price, band coverage and RF output. The ISBN number for Moore’s work is 0-9618882-3-7.

In Closing
I’ve often said that I am not so much the owner, as I am the caretaker of these wonderful icons of our radio history. I’d like to think that I am also the caretaker of the memory of good folks who purchased and built this gear nearly three quarters of a century before. For me it is both a privilege and honor to follow in their footsteps and preserve some small part of radio history for future hams.