Clough Brengle Model 79B
Clough Brengle continued with the 79 series of beat-frequency oscillators with the upgraded "B" version. One of several pieces of new or redesigned units introduced as part of "The 1937 Super Service Line", the 79B now used a 6E5 indicator tube instead of the meter movement found on the "A" to indicate frequency zero beat. Otherwise, the cabinet, controls and switches, and dial were essentially the same. The unit pictured above, is one I purchased off of Ebay early in 2008 and is basically unrestored. Other than a very thorough cleaning, I have replaced the line cord, the cork gasket material that insulates the top of the 6E5 from the cabinet face, and the plastic dial cover. The operation is quite good considering it still has all of the original capacitors, with most of them of the electrolytic variety. Although it takes about an hour to stabilize, onced warmed up, there is surprisingly little drift, and the output is quite clean.