Restauration of DKE38 "Deutscher Kleinempfänger 1938" World War 2 Radio - Page 1
Forum section: electronics / projects

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: February 16, 2020, 02:07:49 pm
content: So I got this old WW2 radio from an old lady. Her husband, who passed away recently, was collecting small radios and now she finaly wanted to get rid of some of the collections of hin. I was allowed to chose one of the radios from the shelve.DisclaimerAs this is a german radio from the time of the second world war there are symbols like the swastika or the Reichsadler all over that thing. Please keep in mind that I am just interested in the technical aspects of the radio and the history that this thing has witnessed.All shown symbols are for documentational purposes only and dont represent my personal feelings, attitude or thoughts in this regard.There were many interesting radios on that shelve, like Philips Philetta, some nice Grundig or Blaupunkts... But one very inconspicious one, the little black box, second row, second from the left, catched my attention.(All pictures enlarge when clicked on)That one is a DKE38, or a "Deutscher Kleinempfänger 1938", made by the Nazi Regime under Hitler as a very cheap alternative to the rather pricey "Volksempfänger" VE301 so that the propaganda could even reach the poorest souls out there. It cost 35 Reichsmark (compared to the 75 Reichsmark for the Volksempfänger) and was reduced to the absolute bare minimum to make something simmilar to a radio. It was considerably smaller, lighter, cheaper and.... well, crappyer than his bigger brother.(The only(?) not enlargeable picture... source:http://www.normei-weinheim.de/DKE38NM/DKE38_V1.html)Sadly I forgot to take some nice "before" pics, so here you have two pictures the lady sent me when I askef her for that radio.Front view. please note the crack on the bottom left of the bakelite case (there is another one, not visible, in the back) and the moldy cloth. that was once nearly white and not stiff as cardboard.The rear view shows the missing backpanel (common and unobtainium), a defective power switch (also common and unobtainium) and a broken off heater series resistor (maybe repairable).Also: Missing Rectifier Tube (common but still more or less obtainable), a cracked speaker mount on the top right, dirt, grime and moisture residue on the chassis as well as some very bad bodged parts in the region of the mains capacitors.Since the cables are insulated by cotton dipped in wax (?), which is absolutely horribly brittle, I decided to replace ALL wires, as far as possible. So I disassembled the radio as good as possible, taking care to not destroy anything that can't be replaced in the process. (Work in Progress picture, again, I missed out with "before" pictures...)This area around the coils I will try to keep the original wiring, as the wires coming from the coils are very thin and I am afraid to break them. Since the posts are pretty solid the shouldn't move and cause troubles. BNut it needs a good cleaning for sure.Another view of the coil assemblySo, after some hours of disassembling stuff the chassis was empty and all parts were more or less free from old crumbly cables:These are parts that are going straight to the trash. please note the funny angle the pins of the mains plug have. I'm sure that is not supposed to be like that.These I will try to refill with new caps to keep the original style. The brown paper capacitor wasn't original so I decided to drop that one and stuff two caps in the other red-ish mains capacitor, to build kind of a double cap. Also not very original, but in my oppinion better than having five different caps bodged in there, as it was before.So I started removing the old stuff from the capacitors shells, cleaning the shells and finding new suitable caps.And this is the result. (the mentioned "double cap" isn't in the picture) Most of the writing and marking is intact.I would have prefered to use black hotglue to seal those new caps in there, sadly I didn't have any. So now those tar filled caps converted to "wax" filled varieties, which is accurate for the time.After that I started polishing the contacts from the tube sockets which I had removed before.Looks like a new socket, doesn't it? Also, the chassis itself got washed in the dishwasher, as well as the case.Nice detail where you see that the radio was built right in war times: the precious brass was short, so they switched over to steel for the contacts - here they ran out of brass contacts for the fuse I guess.I started reassembling the thing, which isn't realy easy as those steel tabs tend to break very fast, as you can see on the right side where one of the pins already broke off while disassembling.You can also clearly see that this radio was made by TelefunkenThe filter choke got cleaned,...... and got a bit of new paint on the metal parts.The variable capacitors got refitted....... as well as the coils.So this is where I am right now.The next steps will be:- Finding a suitable replacement for the tube style resistors (any ideas are very appreciated!)- rebuilding the circuit- modifying the circuit while doing that to incorporate some neccessary fixes (more on that later)- polish the case and repair the cracks- glue in a new loudspeaker cloth- find a way to replace the broken anti hum pot and the busted power switch as well as the back panelHope you enjoyed it so far

author: jonpaul
author_rank: Super Contributor
timestamp: February 17, 2020, 04:30:41 pm
content: Very fine workSuggest to contact Arthur Bauer in Netherlands, at foundation for German Technology, the world's expertJon

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: February 21, 2020, 07:56:36 pm
content: So today Igot allowed to work on the radio by asking the GF very politelygot the time to work a bit more on the radio.My goal for today was to get the tubes glowing, meaning to rebuild the heating circuit - which I did successfullyThe first step to achieve that was to replace the broken power switch. It was pretty hard to do since the original switch is an absolute horrible construction, basically just a metal tongue scraping over another contact - no springs, nothing.Since I can't find any way to replace the tube style resistors with something simmilar and I will HAVE to use some non original parts I decided to accept that also for security relevant stuff like the power cord and the switch - since I already use silikone for the rewiring I think that should be acceptable...However, I thought about how I could mount a switch so that at least the mounting looks... more or less fitting for the time. So I made some micarta from a few layers of recycling paper, dyed thata bit toodark and used that to mount a modern style but pretty safe switch. You can also see the new modern, double (actually tripple) insulated but old-style power cord.Then I started with the rewiring of the heater part, trying to twist the wires as good as possible to accomodate any hum getting induced into signal wires. You can also see the two resistors I put in series of the rectifier tube to dampen the inrush current - one very common problem that regularely kills the VY2 rectifier tube. (by the way: that Weller PCB holder thingy is great for that work!)On the top side I attached the heater series resistor and wired that in place. please note that there is still a little jumper wire missing on the resistor to switch the radio to different mains voltages. I am still looking for an old style cable hook to build that. I will try to get a new VCL11 or look up a way to renew the metallisation on the top as I am scared that it will peel even more in the future.And the final result for today:

author: ebastler
author_rank: Super Contributor
timestamp: February 21, 2020, 09:01:49 pm
content: Hmm -- are you sure about the choice of power switch? I realize that there are different approaches to restoration of old equipment, but this very obviously modern-looking part would be beyond my personal limit.

author: helius
author_rank: Super Contributor
timestamp: February 21, 2020, 09:19:20 pm
content: On the subject of the old wax-dipped cloth wires, I have read some success stories of using silicone conformal coating to reinforce them so they don't flake off. Something likeMG 422B.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: February 21, 2020, 09:42:17 pm
content: Quote from: ebastler on February 21, 2020, 09:01:49 pmYeah, didn't rocker switches only come into use around the 1950s? The standard toggle switch like this would be far more period-appropriate ... and easier to mount.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 21, 2020, 09:43:00 pm
content: Quote from: ebastler on February 21, 2020, 09:01:49 pmI would have used a switch like this:HAHAHAHA!I wanted a rude usernamebeat me by 43 seconds!

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: February 21, 2020, 09:54:56 pm
content: That's how you can spot a true electronics geek. Doesn't care about the periodReichsadlers... but if you usethe wrong kind of switch, you'll hear about it!

author: bsfeechannel
author_rank: Super Contributor
timestamp: February 21, 2020, 11:42:35 pm
content: Quote from: Ysjoelfir on February 16, 2020, 02:07:49 pmBeautiful collection right there.QuoteUnobtainium is a bit expensive these days, but you still can find it insome places.QuoteNice restoration.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: February 22, 2020, 04:01:55 pm
content: Guys, I absolutely aggree with you in regards of the switch. Sadly this was the only one I had available that could withstand mains voltages.Also I am on a very very tight budget right now so I can't buy anything new, not even a switch, if it isn't absolutely neccessary. BUT: Since the switch is held by the DIY micarta I can exchange that anytime without to much hassle which I will do as soon as I get my hands on a better switch.Also, thanks for your comments!

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 22, 2020, 04:43:53 pm
content: my first thought...https://ashleyshaanan.com/portfolio/slang-laboamanger

author: Bud
author_rank: Super Contributor
timestamp: February 22, 2020, 05:19:44 pm
content: This is a shot of the backpanel from antiqueradio.org web site. Is it the Earth/Ground terminal depicted with a little water tap image next to the antenna terminals? Amazing, never seen that type of notation

author: TimFox
author_rank: Super Contributor
timestamp: February 22, 2020, 07:35:48 pm
content: Was that photograph from an album cover? I noticed the Capitol Records copyright notice in the lower right corner.

author: ebastler
author_rank: Super Contributor
timestamp: February 22, 2020, 08:20:25 pm
content: Quote from: TimFox on February 22, 2020, 07:35:48 pm"Radio-Activity" by Kraftwerk (1975).Edit -- forum-relevant content: That album contains the track "Ohm Sweet Ohm".https://www.youtube.com/watch?v=QLwEG3cdeRw.