DKE 38 restoration
 

I long while back I agreed to take a look at this German radio from 1938.
Not the sort of thing I usually work on that's for sure!

The owner said it had been working but is stone dead now. I think it was dropped ?

The bakelite cabinet is in great shape and it has the original grille cloth and back.
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It had been recapped sometime in the past. Looks like the big caps were crudely restuffed, but I have no idea what with.
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The owner included a spare chassis and odd looking VCL11 triode/beam power tube substitute.
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More on the original VCL11 tube here: http://www.radiomuseum.org/tubes/tube_vcl11.html


Phil Nelson did a great write up on this model:
https://antiqueradio.org/KleinempfaengerDKE38.htm

There is filament continuity on both original tubes so fingers crossed they are still good. I really don't want to use that wacky Russian sub if I don't have to.

Right away I discovered one problem. The antenna coupling control is broken. A little glue took care of that.

Everything in this radio is very simple and fragile to keep costs down. I'm being very careful not to do any damage as I work.
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I tested the restuffed electrolytic caps and they appear to have 10uF caps good to 450 volts in them. Even so I'm wary to leave them in no know what really in there.
Instead I installed two poly film 4.7uF caps rated for 450 volts. I'll keep the old caps in case someone wants to reinstall them someday.

The rest of the work done seems sound. A couple mica caps were doubled up and resistors put in series for oddball values, but it all looks OK. Fuse is good too.

So I hooked it up to a variac set to 110 volts and fired it up. Nothing, nada. No power is getting through the radio.

Eventually, I noticed that the funky power switch wasn't working. It's made from some brass strips, and a spring loaded phenolic arm with metal ball contacts.
The idea is that in the "ON" position the balls will complete the circuit through the brass contacts.

Well, one of the contacts is twisted out of position. (Sorry for the blurry photo).
I got it back in position and cleaned the contacts, but it's still not making reliable contact so I bypassed it for now with jumper wires.

Still nothing :(
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More trouble shooting finally led to the fuse holder. The fuse is good, but it wasn't making solid contact with the holder. After cleaning that up, I've got glowing filaments.
A short while later, sound :D

After attaching an antenna, I was able to receive several local AM stations. Not the greatest volume and it takes some careful control manipulation to tune them in.
A little off and the volume drops or it brakes into oscillation and howls.

A funky radio to operate but very interesting piece of history. I'll tidy up my work and add a thermistor to protect the tube filaments.

And odd. :yes:

It makes the Philco 80 look like an EH Scott. :D

Here are a few more photos.

I installed the two 4.7uF underneath the chassis.
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The tiny speaker magnet is surprisingly strong which leads me to believe it's an early use of Alnico. Way smaller than the huge horseshoe iron magnets Philco was using on their farm radios around the same time.

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I spent some time detailing the cabinet before I ship it back to its owner. Here's a closer look at that unusual speaker.

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Speaker basket is made from some composite fiberboard like material.
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Reed type mechanism instead of voice coil
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Bakelite polished up nicely. It's really in remarkable condition.
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Good job restoring a piece of history! It's hard to even imagine all of the propaganda and misinformation that speaker spread to its owners, in its first few years of life. I guess there's so little metal, because it was all directed to making weapons at that time. I'm not sure I would want to own that radio, but it's sure interesting to see the detailed restoration.

A just-prewar German radio, that actually has a Nazi hawk emblem on the speaker housing. Now that is fucking awesome.

I wonder if the emblem is the factory worker's union sticker?

Ok, couple questions. 1. How does it run on 110v unless it was meant for the North American market from the get-go? 2. How does it only have 2 tubes?

Edit: I see the back says it works 110-240v, still then, how does it switch?
Also, I just translated the name. Duetscher Kleinempfanger... it literally means German Small Receiver. Well, the notion that Germans aren't very inventive when it comes to naming things holds true.

If you look at the picture, you'll see a green tapped wire wound resistor. The resistor is jumped out for 110 v operation. To operate it on higher voltages, the jumper was removed or connected to another section on the resistor.
Certain countries in Europe used 110volts in some areas.
The large tube is a dual section, triode/penthode. The circuit appears to be a form of super regenerative.