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AC TRF receiver  with accumulator for the filament of the radio tubes
In Slavonic oak cabinet with black front, black decorative edges and a hinged door at the rear. Four coils can be inserted at the top of the receiver. The feedback is set by means of a movable coil. At the top of the front are the tuning knobs for primary and secondary tuning. The electrodynamic loudspeaker is in the middle, with on the left a milliamp meter that shows the anode current of the power tube. A switch with the positions "on", "off" and "load" is located to the right of the loudspeaker. In the left side are the antenna connection and the connections for an accumulator. The power cord is on the right. At the rear is a gramophone connection.

Martinus Hellingman in 1957

Because of the very high weight (over 47 kg), carrying handles are provided on the sides of the cabinet. The radio was intended for larger spaces, such as cafes, restaurants or dance halls.
The radio has a built-in battery charger, which can be used to charge the 4-volt accumulator for the filament current of the three radio tubes when the radio is not in use. The heavy built-in power supply unit provides the plate and filament voltages for the rectifier and the power tube. Both the radio and the electrodynamic loudspeaker were designed by drs M. Hellingman, teacher at M.T.S Technical School in Dordrecht. An article (in Dutch) that he wrote about the loudspeaker in magazine Radio Nieuws of October 1927 can be read here.
The radio receives medium wave and long wave, depending on the coils used.
The receiver was introduced on August 20, 1928, when the first advertisements appeared and the radio was demonstrated in the auditorium at Groenmarkt 50, Dordrecht. A month later it was demonstrated in the coffee room of the Dordrecht flower exhibition.
The original price was f 650,-.
Data Valves Circuit
Serial number: 43 (on loudspeaker)
Dimensions (whd)*: 58 56  34.5 cm
Made in: 1928
Purchaced in: 2018
Voltages: 220 volts ~ 4 and 1.8 volts -
Weight: 47.4 kg
 

Click on a valve for more information

 

Click on the picture to enlarge

*) w and d: dimensions of the base plate

What was broadcast in 1928?

 

Listen to "'s Wonderful" by Ambrose and his Orchestra, recorded on November 13, 1928.

Back

Back with door opened
Top view of the receiver
Visible are two Philips 4001 resistor couplings, tuning capacitors by General Radio, Benjamin resilient tube bases, a German Wego capacitor, two Lissen adjustable resistors and capacitors and resistors made by Loewe and Dralowid.

Side view
Advertisement in the Dordrechtsche Courant of August 20, 1928 Advertisement in newspaper "De Waterlander", September 15, 1928
Article in the Dordrechtsche Courant, August 20, 1928 Martinus Hellingman on a picture made in the beginning of the twenties.
Article in Radio-Expres, February 22, 1929

This page was last edited on 26.04.2019