hornyphon: DKE 38 B (DKE38B, DKE1938B); Deutscher K

Hello, RM members.  After taking a break for a while, I am getting ready to start my next project - a DKE-38B, from Hornyphon.  Mine looks to be in excellent condition and does not appear to have been worked on before, so hopefully I won't encounter too many problems.

My question is about how to power this radio.  I know I need +90 v., +6 v., and +2 v, but not the current ratings.  What does everyone else do?  Are there repro battery packs available?  Should I just make a small AC-powered supply to get the required voltages?  I'm not even sure what the original batteries looked like.  Any help would be greatly appreciated.  Thanks!

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Michele,

Checking the current requirements for the tube filaments, we find that type KC1 is 2 volts @ 0.065 amp, and type KL1 is 2 volts @ 0.15 amp.  For all three tubes, the total current is 0.28 A.

For the B+, current is drawn between the 6V and 90 V taps of the battery.  The KL1 output tube has a typical anode current of 8 mA and screen current of 1.5 mA (from the datasheet attached to the RMorg page for this tube).  That would also be consistent with an audio power output of a fraction of a watt.  The current draw of the rest of the radio is quite low, as evidenced by the series resistors of 200K and 1M feeding the other circuits drawing from the B+.  So I would estimate about 10 mA total draw from the whole radio; or perhaps a few mA more.

Note that the 0 volt connection of the battery is only for negative grid bias of the output stage.  No current will be drawn from this point.

If you would like to operate this radio on batteries, I would recommend 2 D cells in series for the filaments, with a single 1N4007-type diode (or any other Si diode with at least 0.5 amp capability) in series to drop the voltage to about 2.3 volts.  Alternatively, you could use a 3.6 ohm 1 watt resistor instead of the diode to hit the 2 volt filament voltage more exactly.  Some experimentation with adjusting the resistance a little higher or lower may be necessary, depending on how close to 2 volts you want to get.  I would simply use the diode, since 2.3 volts is unlikely to cause any problem.

For the B+, I would recommend 9 or 10 nine-volt batteries in series, connected between the "+6" and "+90" volt taps as shown on the schematic.  This bank of 9-volt batteries will last a long time at the low current draw of this radio.

For the C- (output stage grid bias), you can use any combination of small cells (such as 4 AAA batteries, or even some watch batteries), connected between the "0" and "+6" taps.  The C battery will last forever -- basically as long as it would last sitting on a shelf with no usage.

If you want to run the radio from an AC power supply, I have designed a few power supplies for typical battery radios and could provide a schematic if there is interest.

Best regards,

Tom

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Thank you Tom for a very informative reply, as always.  My preference would be to run it on batteries for the sake of authenticity, but only if I can find out what the original battery packs looked like, so I could make a repro.  Otherwise, it would be more convenient to just use an AC power supply such as the kit that AES sells:(* see note below) > Kits -> Power Supplies.  From your post, it's clear that this would be more than adequate.  I'd also be interested in your schematics for such a power supply.

If anyone has photos of period DKE-38B batteries, I'd also very much like to see them.  Danke sehr!

* I tried and tried and tried to provide the link to AES here but kept getting an error message "Your post contains at least parts of a link into visible text" even though I *thought* I inserted it correctly and was absolutely unable to figure out what it's complaining about.  So if anyone wants to visit Antique Electronics Supply, you'll have to just Google it or type in w w w . tubes and more . com (without the spaces).

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There are many different ways to design power supplies.  Here's an example (see attachment) of one I did for a Philco model 37-38, which would require only minor modification to work with this DKE.  This general design can be modified to cover a range of different battery radios.

Right now, the power supply is designed for -3 V and -9 V negative bias supplies.  To convert it to a single -6 V negative bias supply, simply remove the 3 V zener (1N5225) and the 10 uF capacitor across it, and connect the 6 V zener (1N5233) to ground directly.  Then the -9 V output terminal will become a -6 V terminal.

You don't need the +135 V output for the DKE, but many other battery radios use that voltage.  On the other hand, sometimes additional lower voltages like +67 V, +45 V, and +22 V are needed.  These voltages are in fact available with this supply by connecting to various points along the chain of 1N4748 zener diodes.  Add a filter capacitor to each tap which is used, just as you see here on the +135 and +90 taps her

Overall, this power supply is a little overdesigned for the DKE, and I would increase the size of the 750 ohm resistor until just before the +90 V terminal falls below 90 V with the DKE running off the supply.  Everything will run a bit cooler if you do that.

To convert the filament supply from 1.5 V to 2.0 V, replace the 56 ohm resistor with a 150 ohm resistor.  I would add a fourth 1N4007 protection diode at the "A" output when using at 2.0 V.  This is a "crowbar" protection circuit to prevent burning out the tube filaments in the antique radio in case the LM317 regulator malfunctions.

Here's a link to a nice LM317 output voltage calculator anyone can use to set the voltage of this regulator to a particular target.

Best regards,

Tom

P.S:  Please use the second attachment, showing 1N4748 zener diodes, not the first (which I can't delete).

• Philco 37-38 power supply (75 KB)
• Philco 37-38 power supply (109 KB)

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Thanks for the power supply schematic.  The LM317 is indeed quite a useful little device.  In fact I just used on last week to connect a 3.3 volt Ethernet board to my 5 volt Basic Stamp.  Rather than add a second power supply, I just used a n LM317 to drop the 5 volts to 3.3.  Works great.

Clearly, someone has done this before.  Here is a photo I grabbed last year from somewhere (unfortunately I didn't make note of where) showing an elegant solution to this problem:

If the owner of this well-made box sees this post and would like to comment, I'd love to give them credit (and find out how they did it :-)

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There have been used a lot of different types of batteries for the DKE. They all look similar like the examples here. There also has been a battery in a grey box named "DKE Batterie". Thesize is similar to the pictures in the link above.

* Incorporating a link into the text:
First mark a word which should carry the link, like I did above with the word "here". Then click on the little globus on top of the editor page "insert link/editing". A window opens where you can paste your link under "URL" by clicking the right mouse button and "insert" as you copied it from the topline of your browser. Close the window an the program will do the rest.

Best regards

Rüdiger Walz

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Michele,

a picture of a typical wireless battery is shown at an offer of tsv-vorrath. It is a type Pertrix battery set and can be customized yourselves.

Regards,

Dietmar

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Thanks to Herr Walz und Herr Rudolph for their kind replies.  I now know that the operative word is "Pertrix".  Searching Ebay for that turned up a few batteries, though not the combined 6 v./90 v. battery the DKE-38B wants.  I think what I will do is just start watching for one of these (such as the Pertrix 271) to turn up.  As a last resort, I'd consider making my own repro based on the photos, but I'd rather avoid all that work if possible.

One final question: the 2 volt wire on this radio is labeled "AKKU".  I gather this is short for "akkumulator", which I think simply means "battery".  Why did they give this wire that label, instead of just "2 volt"?

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In those days, filaments were heated by accumulators (one cell for 2V and 2 cells for 4V), and anodes were powered by batteries. The label AKKU therefore should prevent people from connecting filaments to the high tension battery, in which case the filaments burned out immediately. This occurence, indeed, was not unusual and  was nearly a catastrophy for the listener because tubes were very expensive then.

Regards,

Dietmar

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Akkumulator = storage battery

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