Car radios equiped with tubes.




Radio Mobile type 100 Blaupunkt type ? ZRK type ?

Brand and type: At the left: Radiomobile type 100 - in the middle a Blaupunkt type ? - at the right a ZRK type ?

Produced: The Radiomobile was dismantled from a Bentley 1947 by my friend's neighbour, around 1975. It's probably of English origin. The radio will be of the same age I guess.
The German Blaupunkt should date around 1960, the Polish ZRK looks a bit younger.

Cabinet: All metal plates. The Radiomobile has a wallnut front, and is rather big and heavy. The Blaupunkt could be proudly mounted in a VW beetle, the chromium front on top of the lacquered dashboard. It has four MW-presets, and one for a longwave-station. The ZRK probably was mounted in a few available cars behind the former Iron Curtain: the plastic Trabant, FSO or Wartburg.

The Radiomobile has the speaker built in, and the upper side is fully flat. Maybe the Bentley was prepared to be provided with such a radio, and it had a flat space somewhere underneath the dashboard?.

Tubes: To start with the Radiomobile again: it has impossible types aboard: U82 - KT88 - 2x W81 - X81 - 7C6. Most don't exist in my tube data-books, and I have quite a few of severe age! Besides the whole design is ridiculous intricate, due to mechanical presets. It also has a vibrator to achieve the high tension.
For the Blaupunkt: ECH81 - EF89 - EBF89 - ECF83. The output is done by 2 Siemens power-transistors type TF80/30 (??). This one also has a vibrator for the high tension. It's in fact a mechanical switch operating at low tension. The output is a square wave AC, which is rectified to DC (the B+ of about 200-250V DC needed for the tubes)

The ZRK utilizes tubes intended to work directly at the battery's 12V. So no vibrator needed, these tubes work at 12V only! Mounted are EF97 - ECH83 - EF98 and EBF83. The audio-output stage is one Siemens TF30 power-transistor.
The absence of the vibrator surely was a great advantage, as this part took much service time at the repair shop, as I read in a magazine of the era.
Besides the mechanical noises (buzzing) easily could be heard. Another advantage was that the "mains"rectifier could be left out, the same for the filter capacitors.

Here is a schematic of a radio with tubes working directly at 6V. It shows a rather basic design.The ZRK radio has a EBF-tube, instead of the germanium diode used in this one.
The tubes have less conductivity at this low voltage, but still it works satisfactory.

Power: The ZRK wants 12V, but the positive lead connected to the cars body (ground). The other two: I don't know, they dont work.

Bands: MW/LW for all. The Radiomobile has some presets, all stuck.

Obtained: The ZRK from my brother, who visits Poland twice a year. The Blaupunkt came from a deceased collector who's inventory partially was taken over by Gerard Tel and me.
For the Radiomobile I payed a 75 Dutch guilders in 1985, in the supposition that I could soon repair it. So far that didn't work out. A schematic and tube data would be a great help.

Condition/working: Not too good. Only the ZRK plays well, the other 2 need to be fixed. Especially the Radiomobile will be a tough job.