Homebrew




Homebrew Telefunken speaker Interior

click on 2 pictures to enlarge (the terrible speaker image is yet to be enhanced)

Brand and type: None, it's home made.

Produced: Somewhere in the twenties in France or Belgium.

Cabinet: Oak with ebonite front, looks like made by a pro. Dimensions WxHxD = 43x21x26 cm..

Speaker: Telephone-type Telefunken L636 with paper cone and mounted on a diecast metal foot. Speaker cone diameter is 32 cm. This is a replica for the original was missing, I made it myself. The DC resistance of the coil is 2000 ohm. The speaker is connected in series with the plate circuit of the B406. Of course it's not loud and produces a metallic sound but it's very sensitive. It's cloth-covered cord is still in good shape, the rubber isn't cracked.

Tubes: 3x A409 as RF, detector and preamp, and a B406 as output. All are 4-pin triodes. Coupling between the stages through transformers.

Obtained: I bought it from a guy selling furniture at a flea market; he was unsure if this was a radio. Well, I was very sure about that but didn't tell him. At home I found all tubes dead, it was calculated, and a major construction fault. This radio could never have worked, so my guess is that the disappointed maker moved the set to the attic, after having lots of trouble bringing it to life.

Condition: 8, it's almost in original condition.

Working: 8, considering the limits of the concept. This is a so-called TRF (tuned radio frequency) set, with a single tuning condenser of 1050 pF. As often seen in older gear, square wire is used to connect the components. It uses plug-in coils for different wavebands, and coupling between antenna circuit and tuning circuit. The big center knob on front has a sort of built-in gear mechanism. When playing it I use a longwire of 15 meters at 8 meters height. Combined with a good grounding this gives passably results from about 200 to 2000 meters wavelength.

Connects: A/B supply, speaker, antenna and ground through brass terminals and nuts on the back.

Power: The filaments take 4 V DC, B+ from 50 to 100 V and a 4.5 V battery as the C.

Controls: Variable resistors in the filament circuit of 1st A109 (reducing gain), the same for B406 for volume. Switches for different sets of coils, and a multiple feedback-coil.