Tube Lineup: 6A8, 6U7, 6U7, 42, 5Y3
This Sentinel was found in a friend's attic. The model is most likely a 73BT163 after observing similar radios that appeared on ebay with known model numbers. The label at the bottom of my example reads "6 VOLTS BATTERY OPERATED" but the chassis appeared modified for AC operation. I was able to repair the radio without a schematic and keeping the existing modification for AC operation. The model 73B in Riders under Sentinel Radio Corp. appears accurate, but the original tube lineup differs from my modified example: 6D6, 6S7, 6L5, 6S7, 41 and used a synchronous vibrator. The AC operated version that is identical in appearance to the battery model is a model 72AT163, and can be found in Riders as the model 72A. Sentinel was known for producing a wide array of radios that could operate on all sorts of power sources available during the thirties when 110V AC was not as widely available. The first letter to follow the number in a Sentinel model appears to indicate the type of power supply used. I believe that in general A = AC transformer operation, B = Battery operation sometimes with synchronous vibrator, M = battery operation with asynchronous vibrator and rectifier, U = AC transformerless operation. There are several more modes and some labels are used interchangably or together and I haven't tried to track down the actual meaning of all the letters. Shown below is a mail-in coupon to request more information on the 1934 Sentinel farm radio line.
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