A 1927 ATWATER KENT MODEL 40 BROUGHT BACK TO LIFE by…………

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(Circa 1948)

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(Note: If you just want to hear this old set play some 20’s jazz scroll down to the video at the bottom.)

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Somewhere along the way I acquired an A-K Model 40 which had been put together in 1927 at their Philadelphia factory.  That’s five years before I was put together in Margate City on the Jersey Shore.

From the factory it looked pretty good and the esthetics were a departure from the large wooden sets of the era.  Those in this hobby will frequently refer to old tube sets, particularly ham radio gear, as boat anchors;  this one made the list at 31# though not as bad as my 1947 eleven-tube Hallicrafters SX-43 at 34#.

Over the years, however,  it had not lived well and had also become a mouse condo.

I finally took a serious look at it.  After cleaning out the mouse residue I found that one of the interstage transformers had an open primary.  I thought I could find a suitable replacement but I had also discovered that the power unit condensers (please, I know ALL about capacitors but in 1927 they were condensers ) and the choke were buried under pitch and would require a monumental effort to access.  This dampened my enthusiasm.   Then I spotted another one at a swap meet of the Mid-Atlantic Antique Radio Club and brought it home.  It had all the tubes and was much cleaner so rather than being a parts set it became the object of restoration.

This past winter I fired it up on a variac  with an ammeter in the AC circuit.  I increased the voltage in increments and looked for smoke.  It seemed to be coming up OK when, suddenly, the ammeter pegged so I immediately turned it off.  Probably one of the filter capacitors had shorted so I knew I had to dig in to the tar pit.  I found that someone else had worked on it in years past including breaking through the pitch barrier and replacing one of the filter condensers, the so-called “Blue Spot” shown here.

You can also see the “tar pit” for the other condensers on the right.

I eventually got the old hand-made condensers out along with the speaker choke which looked like some scary 1920’s spider.

The filter chokes are embedded in pitch on the rectifier tube 80 end of the box along with the power transformer.  Fortunately these all ohmed out OK.  Below is seen the capacitors with which I replaced the originals.  The speaker choke ultimately failed and I replaced it with the primary of an AA5 audio output transformer.  I added the resistor shown along the bottom edge of the case to make the total resistance more comparable to the original’s 550 ohms.  The orange-ish cardboard edge is that of a Tootsie Roll box which the prior restorer had used to isolate wires from the metal can sides, and I left it there.  The audio transformer can’t readily be seen but it’s to the left and below the capacitors.

There were two wire-wound resistors on the underside of the connection board, the detector and 1st audio plate resistors;  both were wildly out of spec and so were replaced.  I found that one of the RF filament shunt resistors on the underside of the board was open which surprised me as they are of a heavier wire gauge.  I replaced it with one from the mouse condo.  Finally, the detector and the 1st AF bypass condensers were in the tarpit and were replaced with new caps.

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The power unit then tested OK so I turned to the simpler TRF chassis.  I replaced the grid-leak resistor, leaving the glass resistor (it was open) on top of the chassis and hiding the replacement underneath.  I also replaced the condensers for the filament by-pass, the B+ RF bypass,  and the speaker filter.  These were in tar-filled cans fastened to the TRF chassis.  I used a heat gun to soften the tar and was able to pull out the contents.  One proved resistant to the extent that I cut open the bottom of the can which wouldn’t show anyway when re-secured.   After cleaning out the can interiors I found that they could accommodate the replacement caps.

The volume control is a wire-wound rheostat that reduces the signal strength from the antenna.  The previous restorer most have found a break in the winding and removed some of the low end wiring; he then spread the remaining wires out to fill the opened space.  This made for a scratchy “feel” when turned and would probably lead to another failure so I replaced the wired insert with a good one from the mouse condo.

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All seemed to be well so I connected the power unit to the TRF chassis and brought it up slowly with the variac while watching the ammeter.  It is said among hobbyists that the warm glow of vacuum tubes can make the strongest of us weak.  It’s true for me, particularly as one begins to also hear local stations coming in.  Shazam!

Right click on the image below and click on View Image for a larger, black background image.  (BTW, note that the power unit is labelled as  model 45; that’s what came with it but the TRF chassis carries the Model 40 label.)

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With the set seemingly working I turned to the less technically challenging but all too necessary:  cosmetics.  I had already “cleaned” the TRF chassis including cutting back the tarnish of the years with a Dremel tool and a wire wheel so there wasn’t much more to do.  I’ve seen much nicer work but I’m satisfied with mine.

I then started on the Series E-2 speaker which wonderfully conveys the era.  Its cone was lined with dust dating, I think, from its youth, and the cord was shot.  I turned again to the mouse condo and found that the power cord with its woven brown cover could do the job provided I covered a couple of kinks and frays with heat-shrink tubing.  Done.  Removing the decorative nuts on the rear I was able to remove the cone and transducer assembly so that I could attach the replacement wire.  That done, it was difficult to replace the assembly and have the bolts come correctly through the rear holes.  In the process the cone tore around the quarter-sized center area to which the transducer is connected.  Some carpenter’s glue spread thinly to cover the tear and adjacent area seems so far to have done the job.

Finally, I masked everything and spray painted the breadbox and lid and the speaker with Krylon Camouflage, and the speaker grill and the insert on the set’s lid with Krylon Metallic Gold.  I’m delighted with the results.

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Here’s the “I am pleased video.”  I decided that since the radio was from the 20’s it should be playing music from that decade.    Nice To know these sounds are still drifting around on the internet …. or are they drifting far, far out in the ether???

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My “house transmitter” is  this ebay offering  .  Inexpensive but the signal strength/quality may reflect that.  Unfortunately no schematic or instructions.  Suggestions welcomed to ralph@bergiesplace.com

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I had greaaaat help in tackling this project from all of the questions and answers and original data that are on the internet.  Of particular value is a folksy twenty-one part video series on a similar restoration (Model 37) by someone known as “joernone.”  Tape #1 begins at https://www.youtube.com/watch?v=dio35QiIWm0.  There’s lots of Q’s/A’s at Antique Radio Forums.com, and schematic and parts lists can  be found at http://www.atwaterkent.info/TechData/akSvcDataIndex.html   I also received good advice and encouragement from Dave Slusarczyk, one of the admins for F/B’s Radios from the 1920s

GOOD LUCK WITH YOUR OWN EFFORTS

Ralph   KD2RVA

BergiesPlace.com

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