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Bruce’s Bench 2007

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And now dear readers, another episode of that fascinating radio serial…
Bruce’s Bench

A randomly updated view of what has crossed my workbench in the last few weeks.
Burdened with but a smattering of commentary, this is more of a visual tour.

Click on each photo to enlarge.


December 24, 2007 – Merry Christmas from Maine

Seasons Greetings From Maine

Wishing each and every one of my friends in amateur radio
the very best for the Christmas holiday and for the New Year!

May we all have our own Scrooge moments, and begin the
New Year of 2008 with renewed hope and enthusiasm to better
our life, and the lives of those around us.

In the words of Tiny Tim, “God Bless Us, Everyone!”

73 Bruce W1UJR

November 18, 2007 -Grebe MU-1 Audio Xformer Replacement
Once again, thanks to Gary at Play Things Of Past, another 1920 vintage set has come back to life.
This time it was a Grebe MU-1 Synchrophase which I picked up down in Connecticut last month.
The Synchrophase is a most interesting set, you can read more about it at the CHRS page.
The set was in very nice condition, but suffered from a defective interstage audio transformer.
Gary had the correct transformer at his store, and after an afternoon of testing, stripping and painting,
the 80 year old unit looked like new. In removed the temporary R/C bypass I had installed to test the set,
and wired in the “renewed” transformer. WJTO never sounded better!

November 17, 2007 – Freed and Eiseman NR-5 Audio Xformer Replacement
Thanks to Gary at Play Things Of Past, I found the replacement audio transformer for my Freed and Eisemann NR-5
set. The previous repair shop had replaced the failed audio transformer with a Daven resistance/capacitance coupler.
you can see the glass grid leak resistors on the bakelite block which contains the capacitors. I’d been waiting 4 years
for this, and the AmerTran unit that Gary sent was the perfect replacement. W1FPZ helped out with the correct size
bus wire, and we were back in business. The R/C bridge worked, but the loss of audio gain was significant if one was
using an external speaker.

November 12, 2007 – RCA Radiola III Recap
Thanks to KF9RY, the once aged and tired paper caps and grid resistor in my RCA
Radiola III have a new lease on life. Joseph does an outstanding job repairing these,
installing new caps and resistors inside the tube, keeping the original appearance.
The set now plays like it did in 1924!

October 30, 2007 – Grebe MU-1 Repair
Beautiful radio, but after 83 years it has as defective AF transformer, the primary side is open.
Careful dissection reveled that leads had corroded off and the unit is not repairable.
It will instead have to be rewound, or replaced with a comparable unit.

October 6, 2007 – A Closer Look At The Collins 30K-4 Speech Amp
Next step, get the 30K-4 sounding somewhat decent on the air! The audio section was built for commercial
use, not for fidelity, so the built in audio band pass filter really pinches things off above 3.7 KC.
I monitored the band pass characteristics of the speech amp with the dual channel scope, and AF signal generator,
sweeping up and down the audio frequency band shows where the loss is located in the system.
L301 and its associated caps are designed to be an audio filter, nice for commercial application, but not helpful
for amateur use.

30K-4 Speech amp deck, with the 75TH modulators a light. Plate voltage disabled for testing purposes.

Before the pretty glow is on, filaments just lit, warming up.

Grid input to modulators below cutoff frequency, nice symmetrical waveform. Two channel scope used, one channel on each grid lead.

Grid input to modulators above audio cutoff frequency, note asymmetrical and distorted waveform.

Signal generator used for testing, near upper end of audio pass band.

The testing set up, signal generator and Tek scope on bench, monitoring the grid inputs to the 75 TH modulator tubes.

September 30, 2007 – The Collins 30K-4 T/R Switchbox
Now that winter is on hand, its high time for the return to my favorite band, 160 meters.
I’ve finally got the Collins 30K-4 project, affectingly known as “Old Bessie” somewhat stable,
and just needed to build a simple T/R switching arrangement to mute the receiver during
transmit. As I also operate CW, I wanted a method to easily “unmute” the receiver so I
could hear my side tone. So I threw together a very simple T/R switchbox, something
which matches the 30K finish.

Collins had an optional internal chassis with the 30K-4/5 series to handle this duty,
but they seem very rare. So, lacking the original, I decided to build my own. Rather than
making it an inboard unit as Collins had designed, I decided on the outboard approach, so
I could control the muting operation. As the 30K-4/5 is well equipped with internal relays
for RF switching, my task was greatly simplified. I just needed to design a simple circuit to
switch on and off a set of contacts. I wanted a somewhat versatile arrangement, which
I could use with a number of receivers, so I added both a Normally Open (NO) and
Normally Closed (NC) set of contacts, as well as a switched ground, all brought out to
the rear panel of the enclosure.

A quick search of the junk box turned up all that I needed. A nice old metal enclosure,
back from the days when Radio Shack actually sold parts, a solid 110 VAC Leach
ceramic relay, and some neat old buzzard looking indicator lights for the front panel.
Another late night project, I let the painted cabinet, Saint James Gray in color of course,
bake overnight in the oven.

See you on the air!

September 15, 2007 – RCA Radiola III Variometer Repairs
Fired up the old Radiola today, and discovered that two of the small black stranded wires which connect the
variometers for the Regeneration gain and Station tuning were broken. What did you expect after 83 years?
By loosening three of the set screws, and unsoldering one wire, I was able to remove the Regen coil from
the unit for repair. The small clock spring on top of the coil is attached to a pivot pin which will pull right out
of the coil, releasing it for service. Once I managed to remove the pivoting coil, it was a simple matter to
strip back and repair the broken wire lead. It was a small detailed little operation, and I used heat shrink tubing
to minimize bending damage in the future. I suspect the wire will need replacement soon, it was the green/blue
color of copper oxide. I am not certain what causes this internal corrosion, but each of the small wires, attached
to the coils, displayed the same damage. I wonder if something in the wire insulation is either causing, or
accelerating this problem. The wire insulation seems to be a oil impregnated braided cloth covering.

September 11, 2007 – 4″ Radio Dial Needed for Homebrew Transmitter
I am looking for at least one, ideally two, of the following radio dials for my 1934 homebrew transmitter.
The knob measures 4″ in diameter, and has a threaded brass collet which is mounted through the center
onto a shaft. I can not say for certain the manufacturer of the item, but it does have some markings on the
rear of the knob. You’ll note that mine is currently cracked, the result of a fall onto my workbench.
I would be most grateful to any assistance you can provide.

September 5, 2007 – 1924 RCA Radiola III Arrives
The RCA Radiola Model III was introduced in 1924. Priced at $24.50, it became very popular and sold in the thousands.
The Radiola III is a battery-powered regenerative type receiver, using two type WD-11 tubes.
One tube acts as the detector, the other as an audio amplifier. It receives frequencies from 470-1540 kilohertz,
approximately the same as our modern standard broadcast band. This is a small radio. Its cabinet is almost cube-shaped,
measuring about 8 inches wide, 7 inches deep, and 7 inches high (including the height of the tubes).
The thick cloth cable coiled to the left contains the battery wires. The cabinet is made of solid mahogany.
The faceplate and large knobs are made of black Bakelite. Other controls and fittings on the faceplate are nickel plated.
Like many radios of the time, the Radiola III was designed for use with headphones.

August 18, 2007 – A Visit to the Liberty Ship John W. Brown
Today was a most special day, a visit to one of the two remaining Liberty Ships,
the John W. Brown. The Liberty ships were cargo ships built in the United States
during World War II. They were British in conception but adapted by the USA,
cheap and quick to build, and came to symbolize U.S. wartime industrial output.
Based on vessels ordered by Britain to replace ships torpedoed by German U-boats,
they were purchased for the U.S. fleet and for lend-lease provision to Britain.

Eighteen American shipyards built 2,751 Liberties between 1941 and 1945,
easily the largest number of ships produced to a single design. The John W. Brown
has thankfully been saved from the ship breakers, and is now a floating museum.
But she is not just a static display, but rather a active ship that can and does
steam from port to port under her own power. You can find out more about the
Brown at

Yesterday, during our six hour cruise around Casco Bay, we were treated to
classic big band music with a live band played on top of one of the massive
cargo hold covers, Glenn Miller and Tommy Dorsey favorites were played.
President Roosevelt and General MacArthur came onboard, and were warmly
received by the many World War II vets. Later, off the coast of Maine, the ship
was attacked by World War II Japanese planes, which the crew of the Brown
attempted to fend off using deck guns. The Japanese planes were finally driven
off by the appearance of two US World War II fighters plans. Near the end of the
cruise Abbott and Costello put on a excellent comedy show in one of the forward
cargo hold.

I spent a good part of the time on the bridge, and quickly made friends with
some of the many older navy vets. Later, I was treated to a personal tour of the
radio room of the Brown, which appeared as complete and as functional as the day
it left dock in 1942.

In closing, I would highly recommend the “Living History” cruise from the all volunteer
crew on the John W. Brown. It is like a trip back into the 1940s, complete with the
period music, and a delightful way to spend a day.

August 11, 2007 – The Radioactive Boy Scout
Yet another goodie arrived today, something which I had been
waiting for, an interesting new book, “The Radioactive Boy Scout”.
The summary follows, suffice to say, this promises a most
interesting summer read!

“On June 26, 1995 the people of Golf Manor, Michigan returned
from work to find a federal EPA crew dismantling a potting shed
in Patty Hahn’s back yard. In subsequent days, the crew,
wearing protective suits, carted away the refuse in sealed barrels
emblazoned with radiation symbols. The EPA workers refused to
disclose what was happening, only offering vague reassurance
that everything was ok.

In truth, David Hahn, a 17-year-old aspiring Eagle Scout, had
constructed the rudiments of a nuclear breeder reactor in his
backyard and had contaminated himself and the immediate area
with potentially deadly radioactive material.”

This was originally a subject of a Harper’s magazine article,
the link to the Harper’s article appears below.
Link –>

August 10, 2007 – Begali Graciella Vertical Key Arrives!
It was sure worth the wait! My spiffy new Graciella key arrived today, and
what a beauty it is. The guys told me that I would love it, and it sure looks
nice sitting next to the Elecraft K2.

The Begali website states “The Graciella Vertical Key was designed to be
the ultimate vertical dual-lever paddle. The feedback from CW experts
around the world and the experience that we gained with our other
magnetic paddles have been combined into a revolutionary design of
stunning beauty.

The Graciella uses the highest quality bearings, gold or palladium plated
components, aircraft alloy for moving elements to reduce their masses and
maximize responsiveness, micro-threaded adjustment screws for the contact
gap and the magnetic tension, and a stereo jack for the connection cable.
The Graciella has massive gold contacts for the ultimate in reliability.

Although the footprint is only 3×3 inches, smaller than our other paddles,
this is a heavy key, weighing in at about 3.5 pounds – so you can be sure
that it won�t walk around on your table. That weight is the result of heavy
duty components that were designed for a lifetime of reliable service.

In case you want your own, the Begali website is located at
You can find reviews of the key on eHam, at



July 14, 2007 – General Radio Co. Wavemeter from Union, Maine Hamfest
Followed me home from the Union, Maine hamfest today!
Built in 1944, but appears to be new in the box, covers 16 KC to 50 MC, and is complete with all
coil sets and instruction sheets! The seller said he found it at the dump in Paris, ME.
Sure it is no longer practical, but man is it pretty!


July 7, 2007 – Visit from Tim W1GIG and John W1FPZ
I was given a most gracious gift from John W1FPZ, a replica 1930s Gross transmitter which he built for Marshall W2ER SK.
Thanks to the efforts of Tim W1GIG who transported the unit up to Maine, and John’s kind gift, the unit now has a
good home, and should be a regular on the AWA Contest circuit.

Update – I need some parts to get this unit fully restored and back on the air, please see my Replica Gross Transmitter

Tim W1GIG and John W1FPZ with the Gross replica

May 8, 2007 – Visit from Louis VA3AWA and John W1FPZ

March/April 2007 – Elecraft K2 Build

March 2007 – Elecraft K1 Build

February 2007 – Elecraft KX1 Build