RCA U-70 UHF Selector

This was RCA's top-of-the-line UHF converter in 1953. It tunes all 70 original UHF channels. One- and two-channel units -- models U-1 and U-2 -- were also made. The U-70 must have been a pretty good seller, because they are still fairly common 50 years later. The U-70 has the most elaborate circuit of any converter I've seen, with 4 tubes and many tuned circuits. The usual 6AF4 oscillator is followed by two 6CB6s as the IF (channel 5 or 6) amplifiers. A 1N82 semiconductor diode serves as the mixer, and a 5Y3 rectified the high voltage from the power transformer. UHF channels 14-83 were covered continuously in the large fan-type dial. The chassis number is KCS-70. A KCS-701 chassis variant replaces the tube rectifier with a selenium stack.

The styling is very consistent with RCA table model radios of the period, though by this time relatively few table radios had wood cabinets. I have seen publicity photos of a variation on this model, with the dial on the top surface, but I have no evidence that it was ever produced. Both Mahogany and Blonde wood (veneer) cabinets were available for this model. Blonde wood was popular in the 1950s: besides this RCA model, it shows up in my collection in the Astatic AT-1B and Bogen BB2 boosters and the Motorola TC101B UHF converter.