TELEFUNKEN 40W

The 40W is a legendary German broadcast radio receiver manufactured by Telefunken between 1929 and 1930. It has a unique construction where it uses a thick compressed paper baseplate instead of a metal chassis. Electrical connections across the underside of that plate are partially achieved using copper strip conductors. This form of circuitry foreshadowed the modern printed circuit board (PCB), which did not become a standard manufacturing method until the 1950s. 

The bakelite housing is large (53 cm wide) where the lid is locked with a key that also operates the on/off switch. The receiver has 4 bands covering MW and LW ranging from 150 to 1500 kHz  The circuitry uses the Tuned Radio Frequency principle with regeneration. Volume is manually managed by balancing the antenna matching knob (bottom left) against the feedback/regeneration control knob (bottom right). A fine-tuning lever sits next to the main tuning knob to manually adjust the synchronisation of the internal variable capacitors. It basically rotates the chassis part of one of these capacitors.  

The receiver was designed to pair with a Telefunken Arcophon magnetic speaker. I have it working well with a 2000 Ohm Philips model 2032 speaker.