Restoration of a Grundig Heinzelmann by Dietmar Ehrhard –
Translated by Kathrin Henkel
The famous Heinzelmann-radio-kit
There it is, the Heinzelmann, not (yet) pretty, but rare.
I bought this radio in October 2018.
Since I did not want to have it sent by post, for fear of a “Litter consignment” treatment, I had to pick it up myself.
Well, I had to travel to Traunstein at the Chiemsee, which isn´t merely around the corner.
So I boarded the Eurocity-Train from Frankfurt am Main to Klagenfurt that stops in Traunstein.
I started early in the morning, meeting the seller midday at the Traunstein-station. Then I packed the Heinzelmann and a Körting for my colleague Wolfgang.
How that was possible by train?
You need a retireeˋ s trolley, packing materials, some cardboard and lots of tension straps.
Getting on and off the train was a big struggle and I got weird looks for free. But everything went well.
Over two and a half years later it was finally time I breathed in new life to my Heinzelmann.
Let’s go!
…the start of all Grundig products.
The backside reads: Rundfunk-Baukasten [Broadcast-Kit] „Heinzelmann“ und „RVF Elektrotechnische Fabrik Inh. Max Grundig“ [Electrical engineering factory owner Max Grundig].
So it’s a (Toykit) broadcast receiver of the first ever kind after the war.
By declaring it a toy Max Grundig managed to disregard the allied ban on the production of broadcasting devices.
RVF started selling a little few devices in 1946 and only got noticeable sells in 1947.
My radio is device number 11173. According to my research there were 9560 radios sold by the end of September 1947 and 11515 sold by the end of October 1947.
By the end of 1947 you could buy already built devices too.
Let’s check the interior to find more clues about a production date.
Bingo!
The rotary variable capacitor is stamped 8th of June 1947.
The mounting plate is made of black cardboard, the tubes are Wehrmachts tubes RV12 P2001 und RV12 P2000.
The RV12 P2001 is marked “R” for armed forces. Since it’s a controllable HF-pentode for FM frequencies, it is assumed that it was formerly used for an armed forces radioset.
With all of this I’m certain that the Heinzelmann is dated October 1947. The set was probably built mid 1947 and sold early October, without tubes.
Now that we have history out of the way, I’ll start restoring.
It’s a do it yourself kit so let’s make it one again. With a device this old, it would be necessary anyways to fully take it apart.
This might be how the kit once looked:
The capacitor block and the other capacitors have capacities that are … Let’s not mention it.
So they need to be emptied and newly filled. Hot air easily compels the innards to simply float away. First of the capacitor block:
Now just refilling and resealing the rest of the capacitors and they’re as good as new.
Just the longer wires tell the difference.
Did you know that old radios can get a hunchback?
Some hard to notice stiffening and matte black lacquer rejuvenate the whole look.
Now we can rebuild!
The device has been altered before and there’s a wrong series resistor for the heater that is built in. The original is gone.
So what now?
Since the mounting plate had two electrolytic capacitors at 8 µF built in, I decided to use one electrolytic capacitor at 2 x 8 µF and then use the free space for another solution
A small heating transformer is hidden in a silver pot and placed in the free space.
Two silver pots before and after? Great!
The resistors were tested and cleaned, all pieces put back and everything rewired.
And well then there’s the other problem…
The casing won’t win any pageants soon.
Careful and thorough sanding helped rewind time.
Some lacquer, more sanding and more lacquer revived the wood’s old shine.
Wood colour and grain are beautiful again.
The dial had to be replaced too. It was a replica made of foil behind glass stuck together with tape.
My colleague Hajo used Photoshop to create a usable graphic. Thanks for that!
While the new acrylic pane isn’t fully opaque, it’s still a great result.
Mounting plate done, speakers…
Speaking of speakers…
Here my colleague Wolfgang was irreplaceably helpful. He handmade a brass screw since the original was broken. It was needed to fix the speaker chassis.
He also rewound the burnt output transformer.
This is an especially hard task, as you need veeeery thin wire that is wound around the coil veeery many times to reach the needed resistance for the RV12 P2000. Thank you Wolfgang!
And now here’s the payout for all the effort, Nice, is it?
But a Heinzelmann isn’t just for looking at, but for listening to.
So here is a video with fitting music:
- The original text in German: Heinzelmann
- Click here for information on the Radio-Museum Linsengericht e.V.
- For further information, do not hesitate to contact us at post[at]radio.de or leave a message at +49 6051 7869570, we will contact you as soon as possible.
- If you would like to visit us and see the Heinzelmann, be aware that we mostly operate in German. If you do not speak German, please inform us of your visit beforehand, so we can arrange for an English speaking guide. We currently sadly cannot offer more languages.