Bulova 140 Clock Radio

The Bulova 140 is your basic All American Five radio with a a mains-driven clock on the side.

Tube lineup is 12BE6, 12BA6, 12AV6, 50C5, 35W4 which is the definitive AA5 tube lineup from 1946.

I don't have a schematic for the Bulova 140 but here's a representative schematic from Wade's Audio And Tube pages which is no longer on Angelfire -- fortunately the Wayback Machine kept a copy.

Other radios with the same lineup

• Toshiba Kanariya K, 5YC-763
• Motorola A2N, 5H1
• Lots of Japanese midget sets.

Here's a schematic of a radio using a 12AT6, which is a lower gain version of the 12AV6.

Making an AA5 work

AA5s are ... interesting. To save cost, there's no mains transformer, the radio runs straight off 120V AC (All American Five. 120V 60Hz. They can be made to run on 220V 50Hz, more about that later). This explains why the tubes have strange numbers like 50C5 and 35W4 -- the 50 and 35 are the filament voltage. The five filaments are wired in series to run off 12 + 12 + 12 + 50 + 35 = 121V.

So why not design the tubes so that they all run off 24V each? 5 x 24 = 120V, right? Well, in series, the current through each filament is the same (150mA in this case), so the tubes that need a higher wattage filament to support a higher anode / cathode current needs to drop a higher voltage. So the power tubes (rectifier and audio amplifier) have higher voltage filaments.

This is just one of the many subtle bits of genius that makes up the AA5 design. Read Max Robertson's very good explanation of how the AA5 works. Wrap your head around the dial bulb weirdness.

Anyway. I bought this radio off of eBay for $23 and change in August 2014. Shipping was obviously bumpy.

Making an AA5 work on 220V

One can use a transformer, of course, but there are better ways.

Making a 60Hz clock keep time on 50Hz mains

This is the difficult part. ESP Labs will show you how to build a small AC PSU at the right frequency. You might also want to rewire the clock motor