Bread bin home build 20's Parts

 

A 1920s style radio and parts in a 2019 bread bin with folding see through lid. My design was based around the General multi-coil 3 function unit; that's aerial loading, grid coupling, and reaction coils with 3 control knobs all built into one unit.

L1, L2 and L3 all housed in a General made unit

The unit is shown here with face plate and control knobs removed. I was lucky to find this on line cheap as part of the Bakelite facia was broken, but I didn't need it in this job it was really built for a wooden front. In my design you need to open front to tune controls, and closing them after keeps dust away and also allows you to see internal parts, about 20 in all if you add connecting screws. The circuit above shows the 2 valve design. Coil 1 receives the signal and had a tapped connector that then feeds it across the 300pf tuning capacitor.

where it is tuned to the required frequency and fed by coupling capacitor to the G1 of the Triode valve that has a Grid Leak resistor (2.2M) negative bias to chassis causing the valve to rectify the incoming RF signal and amplify with the help of feedback from coil L3 that is a Trickle Coil, that means it's loosely rotated inside the aerial coil to a point where feedback is controlled without whistling. 

Hard to capture picture of Trickle Coil inside main housing of General made coils

I've added a photo of the 2 valve holders that I restored, before and after. They were silver plated copper, so it cleaned up nice, the undersides had see through insulation.

Lots of old parts survive, vintage radios get scratches or wood worm and the innards are sometimes kept. I thank those hoarders with all my heart, lol 

The wooden bread bin was around £20 from a well known retailer, designed for a rustic look.

The coil tap switch is shown here, all well made and expensive at the time I expect. I made a plastic strip for the connecting terminals at the rear and used brass nuts and bolts, not Philips screws (too modern) trying to get the feel of a period build. I'm not sure how far back curved bread bits go back but I remember having one in stainless steel for a wedding gift, only to be confiscated by the DTI in a studio raid once when I had used to as a screening can for two tape decks, lol

  This photo just shows me placing parts inside so they could be  seen from front and also gave enough room for the 18 SWG copper wiring. I drilled 2 holes in left side for speaker wires, but all the others were contained at rear inside.