1952 Zenith H723 AM-FM Table Radio

Early AM-FM table radio, with Bakelite cabinet featuring typical very-cool Zenith styling of the era. My wife picked this one up in January, 2000 while vacationing in Florida and very kindly brought it home to surprise me!  She found this at a flea market near Fort Myers. Overall it was in very restorable condition. Cabinet was excellent and the interior was relatively clean. The original selenium rectifier unit had naturally developed a high internal resistance, and was replaced with a new silicon unit, with a small series resistor to keep the B+ voltage down to normal. Restoration was uneventful, except for loud, crackling noises. This radio was suffering from “Silver Mica Disease”. This is intermittent breakdown of the mica capacitors inside the intermediate frequency transformers due to aging. This is a relatively common problem in these capacitors of the era, as they are not sealed, but exposed to the air. The only way to fix this is to remove the transformers with the internal problem, dismantle them, and very, very, carefully remove the mica capacitor plates. There was lots of room inside the transformer cans (in this case) to install new, hermetically sealed silver mica capacitors inside. I had to do this with 3 of the 4 shielded transformers which added about 4 hours to the restoration process (Total, 20 hours)

Before and after images-click on thumbnail for large view:

Cabinet Front
After Restoration

Zenith H723 Cabinet Front-After Restoration

Cabinet Front-Top
Before Restoration

Zenith H723 Cabinet Top-Front-Before Restoration

Cabinet Front-Top
After Restoration

Zenith H723 Cabinet Front-Top-After Restoration

Chassis Top
After Restoration

Zenith H723 Chassis Top Front

Chassis Underneath
Before Restoration

Zenith H723 Chassis Bottom-Before Restoration

Chassis Underneath
After Restoration

Zenith H723 Chassis Bottom-After Restoration