Atwater Kent 44s
 

I decided to go whole-hog on restoration and purchased two Atwater Kent
model 44 radios and speakers off eBay. They are in different shades
of decrepitude but both have a full set of tubes. I figure I can get
enough unique parts to make one work and then if desired scrounge
up ones to do the remaining one.

I wanted an AC set, but of course these have the tar-box power
supplies. I've seen instructions for removing the tar but I can't
find them now. Does anybody know where to look.

Why was it in tar? Is the tar soluble
in chloroform (for cleanup)? Could one restore without tar and
install a "pan" of tar on top of the innards to make it look somewhat
right?

How big is the tarbox? I don't have the objects yet. It would be
good to do the de-tar in a lab oven in a hood, but it may be too big.

Doug McDonald

Well, I FINALLY found the instructions I mentioned. They are nicely complete.

But that does not answer the question "why tar in the first place?"

They wanted to keep moisture out, I believe. All that was quickly got over with after the early thirties. In the case of RCA, they didn't want anybody snooping around in their internal circuitry of the "catacomb." I'd just get rid of the tar and forget about any kind of filler: not really needed.

I'd test the internals first, a surprising number are still OK. No electrolytics, just wax caps. (1-2uF) Typically, the 2 resistors under the terminal strip are open or increased in value. I'd definitely install a fuse in the AC line though..

I would still go through and replace the filter caps in that power supply. I ran my model 42 on the original caps until they shorted one day, fortunately taking out the rectifier tube instead of the transformer. You can chip away enough of the tar to expose the wires going to the capacitors. Clip the wires and splice in the new caps. That way you don't have to stink up the house trying to melt out all that tar.

And if you do replace the filter caps, you can use big mylars instead of electrolytics and they will work the same way the originals were intended without the deterioration of electrolytics.

I got my first (I bought two) E2 speaker yesterday. These are of course
high impedance, perhaps 1 to 2KOhm (a guess). I checked it for continuity
(good) then hooked it across my AV receiver main left channel, leaving
my main Hafler power off turned off. I got weak sound at a high level
on the control. I loaded up a long music file in Audacity, made it mono,
and inverted the left channel. I hooked up the speaker across the two
hot terminals of my big main amp, now it sound plenty loud.

A close inspection leaves open the question of whether it has been
reconed. These things have an "open" outer cone edge, no rubber support.
A close look shows that the cone was made by wrapping a sheet of stiff paper
into a cone and gluing it together. But the attachment to the "works"
looks awfully neat, and a close inspection of the gap at the outer edge
showed lots of very very old dust and lint in it. Does anybody know if
the original cone in these was seamless or seamed?

Now as to the sound! I thought these things had a characteristic
bad sound. Not so. It just sounded like any old 12 inch or so cone speaker.
So I had Audacity generate a correctly out-of-phase-channels 100-10000 Hz
sweep and listened. There are some incredibly large resonance peaks
in the lower frequencies, at higher frequencies no big ones, just rough response.
The useful frequency range is about 150-5000 Hz. At some of the lower
frequency resonances the sound is essentially ALL distortion, some 2nd
harmonic, some third. Odd.

Has anyone else ever tested one of these? If so, is that what you heard?

What's the best web site for very old radio restoration discussions?

I have tested a few "Moving Iron" driven loudspeaker. The first Rice-Kellogg speaker (Radiola 104?) was a huge improvement.

I am trying to improve a Radiola 100 speaker which has resonances between about 500 to 800Hz and not much top (above 2500). I am sure it can sound better. But then maybe that was it?

On reflection, one can understand why acoustical audio playback lasted well beyond electrical recording!

I am in the process of restoring a Victor Cromwell phonograph from early 1926. It uses the Radiola 100 moving iron speaker similar in design to the Atwater Kent E. Although the electronic Victor Cromwell was more expensive to initially purchase in 1926 than an acoustic Orthophonic Victrola, the Orthophonic Victrola I imagine has better sound. I will better judge if I get the Victor Cromwell to fully work as it should.

There is a bigger radio knowledge base here. http://antiqueradios.com/forums/index.php

The first A-K 44 (60 Hz) arrived today. I suspect a barn
or leaky attic. Its rusted badly.

But there is good news. Of the 8 tubes, 6 are good, including
the 71A and the 27. The spare 27 was not wrapped for shipment,
just loose in the set (!) and smashed. Two 26s are bad,
one gassy and one with very low emission. Three hours at
10% higher filament voltage helped only a little. A third 26 is
just a little low but should work. Also, its the new-style tar-pit
with the separate capacitor box.

Then there is the very bad (or expensive) news: the power transformer is bad.


How does one remove the resistor board from the power supply?

I worked on a similar AK and the resistor board was held in place by a couple of nuts; but, yours might be different.

The bad xfmr is very bad news and it might mean the end of the line for the radio unless an organ donor can be found. This probably happened due to shorted capacitors.

The power transformer is not bad, the ballast is bad.

In any case the transformers can be rewound for $160 if that (i.e.
an expensive radio!) is your "thing".

But then what about the ballast? I MAY be able to fix it with my spot
welder.

Are they available? Could I just use a fixed resistor? It looks to
be wound with Nichrome wire or plain nickel. These have hugely
different temperature coefficients. Presumably a light bulb
of the correct type would also work.

Does anyone know what the resistance is under working conditions?
Does anyone know what the voltage across it is under working
conditions?

Today is tar-pit melt day.

The strange open mica capacitor is good. The wire resistors
on the board in the power supply are good. Two of the wirewound
grid resistors are bad. Is the inductance of these of any importance?
All of the glass resistors are bad ... in fact, the glass is loose
so I removed the carbon and cleaned them up so I can leave them
in place.

Oh yes ... it looks like the case inside was painted tan. Does anybody
know if that is true, or what it really was? What about the steel
mount for the tube sockets?

Doug McDonald

Does anybody know what the correct B+ voltage is, measured a the output
of the power supply at the input end of the 3000 Ohm resistor in the plate
circuit of the RF amplifiers?

While awaiting new caps I removed the audio choke from its tar pit safely.
I also removed the two small tar boxes from the chassis itself asn I intend to
restuff them.

This radio was very rusty. I finally got all the screws loose. I've decided
not to try for a full cosmetic restoration of the chassis but am just removing the
worst of the rust and grime. Its beginning to look better.

Now for the question: what should I do for the case? The majority
of the outside of the case and lid simply looks poor, somewhat rusty in places,
with good paint in others.
But the area around where the lid fits on is exceedingly rusty on both parts.
Also the interior of the case is exceedingly rusty.

I tried Naval Jelly on a few spots on the inside and even after some
hand sanding it does not give clean metal.

The question is ... what should I do? Should I try removing all paint and
rust, or just the rust, and then repaint? Or what? Getting the rust off
will take either bead blasting or lots of hard hand scrubbing. What do
people do about the residual paint?

I've completed the job on this radio, my first restoration (as opposed to simple
repair, just replacing bad electrolytics). I replaced all caps except
the grid leak mica and all the resistors except the two 350 Ohm good grid ones.
I removed as much rust as possible without sandblasting, and repainted the outside
with VHT Wrinkle Black, the center part on top with Rustoleum Ultra Gloss Metallic
Gold (an awesome beautiful paint!) and the power supply lid center part and case interior with a Rustoleum flat brown that matches the old power supply lid center
very well. All show signs of the old rust but pretty nice. The chassis still looks
diseased (I considered painting it Rustoleum Ultra Gloss Metallic Silver, but didn't.)

I have a question about sensitivity. I didn't expect great sensitivity, and it isn't,
at least by modern standards. Only the four local stations come in usefully,
and one only by day. At night one can hear, faintly, a couple of other stations.
This is with a 40 foot outside wire. Is this normal?

Doug McDonald