Astatic AT-1
Based in the Lake Erie resort town of Conneaut Ohio, the Astatic Corporation was a microphone and phonograph-cartridge maker founded in the late '30s by two Ham Radio operators. No doubt because their town was too far away from TV stations in Cleveland or Buffalo, the engineers came up with a high-gain TV signal booster, which they offered to the world as their model AT-1. It was very successful, remaining in production for years after more modern units had been designed. The large, bentwood slope-front cabinet (available in mahogany and blonde) and great tuning flexibility must have been selling features.
The circuit used four 6AK5 tubes -- two each for the high and low TV channel bands. Ganged variable capacitors are used to tune each tube's grid circuits, while the plates are broadbanded. A gain control (a rare feature) varies the voltage to the tube screen grids. The power supply consists of a transformer for the tube filaments, and the usual half-wave selenium rectifier for the high voltage, with a "hot" chassis.
The first one of these boosters I acquired rattled badly, and upon opening the cabinet I discovered the results of one of the failure modes of the selenium rectifiers. An early semiconductor, selenium rectifiers are fairly robust, but slowly degrade and often fail by overheating, with the release of acrid (and toxic) smoke. This one overheated to the point of meltdown, destroying itself and melting a hole in the steel chassis! The only remains were pieces of scorched wiring and melted metal. I'm glad I wasn't around when that happened!
Updated January 30, 2007