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Four-valve TRF battery radio
Wooden frame with ebony faceplate with silver engraved lettering. The chassis was once part of a larger cabinet, but I found and original smaller cabinet, also intended for this chassis.
The device has a HF-tube, a detector tube, a LF tube and a power tube. It is therefore a TRF receiver, the LF tube and the power tube are  resistance coupled. There are no rheostats for the filament voltage. The volume control (a 50 k rheostat) is located between the LF tube and the detector tube, a modern solution for this period. The speaker has a choke circuit (a Ferrix choke plus a Hydra capacitor), a safety feature that prevents high voltage on the loudspeaker terminals.
The knobs from left to right: primary tuning with fine tuning, wave length swich with reaction control above it, secondary tuning with fine tuning, rheostat for volume control. Connections at the back: loudspeaker, jacks for the plate currents or a battery eliminator, filament accumulator, earth and antenna.
Included is a bulky power supply unit, that not only provides the plate currents, but also the filament voltage.
Data Valves  
Serial number: none
Dimensions (hwd): 22.8 x 51.4 x 23 cm
Made in: 1927
Purchased in: 2015
Sold in: 2022
Voltages: 4, 45, 135, -1,5, -15

Click on a valve for more information

Wiring diagram

What was broadcast in 1927?


Listen to "At the Jazz Band Ball" by Bix Beiderbecke and his Gang, recorded in 1927

The top of the chassis
The back of the chassis
A look inside

Advertisement in Luistergids, October 22, 1926


Advertisement in Nieuwsblad voor Gorinchem en Omstreeken, November 26, 1926

The power supply unit

The power supply unit seen from two sides.
On the left, the Ferrix transformer for the plate voltage, a Ferrix choke, a double TCC smoothing capacitor for the filament current and a Ferrix heater transformer. On the right, a Kuprox metal rectifier for the rectification of the filament current, TCC smoothing capacitors for the plate voltage and a Ferrix choke. Above the Kuprox rectifier, a helical correction resistance is visible.

Deze pagina is voor het laatst bijgewerkt op zondag 25 december 2022