Back On the Farm - Radio

 - or What to Listen to When the Power Goes Out

After all, we do live on a farm, or at least that is what the sign says coming up the drive - Tree Farm.
And, had anyone lived here prior to 1950 or even later, there would have been no commercial power. One of my neighbors still has his wind generator spinning in front of his house - I need make him an offer on that one.

The Rural Electrification Act of 1936 provided loans to extend the electric grid out to farms and rural communities. Like broadband internet connections today, there had been little interest in spending on infrastructure where few customers existed. Earlier, "farm radios" had to run on wind generators or batteries.  

Above: A Philco battery "jar" which would yield 6 volts DC when filled with acid and lead plates - until it was knocked over by the dog.

Above: A Parmak brand "DeLuxe" Model 525 manufactured by the Parker McCroy Co., which is the same company that built the fence chargers we use to keep varmits out of the garden. So they are still in business, still selling farm equipment.

You can usually tell a farm radio from the lack of a visible power transformer and the metal can that houses the noisy vibrator  power supply.  Noisy meaning - It  hums, or buzzes and it can generate some RF hash especially if the little mica cap across the output is bad - and they often are since this is a very rough life for even a mica cap.

All of this makes them less than ideal for collectors that wish to display a working radio. AND it is likely that the power supply no longer functions. Which causes some people to reason "Rather than fix the supply that runs on batteries - that I don't have, let's convert it to  - who knows - something else". These conversions usually result in a radio with missing or damaged parts, which was the case here.

Before I go on, You should know, that this is an uncommon radio. So much so that it does not seem to be correctly identified  on any of the usual internet ID pages. The name seems to be the source of confusion. Now that you know what it is, the schematic can be found in Rider's 13-2. 

To make things more interesting, the schematic shows the source voltage with reversed polarization (positive. ground). DON"T do that! While the syncroness vibrator supply will run with the input voltage reversed the filter caps across the output won't - nor will the radio.

Beside needing caps and resistors, this supply had half of the primary winding open. So it was 3/4 good - or entirely bad, which ever you prefer.

​Being basically lazy, I chose to only fix only the bad winding.

Yep, I used a socket to push the primary winding out of the secondary - this only works part of the time and heat may be required.

Fortunately the open winding was on the outside of the primary ( the outer 1/2 up to the center tap). Had the break been on the inside half, I would have rewound the entire primary.

The magnet wire did not show the typical corrosion or burns from overheating. Instead  the outer windings had become brittle, breaking many times as I unwound the failed 1/2 of the primary.

Now all I had to do was squish it back in there.

Before and After: The chassis got all of it's caps restuffed.

Chassis reassembled.

For a 5-tube battery radio, performance is pretty good on the broadcast band. The cabinet looks OK but it was never all that "DeLuxe".

Coming up: Back On the Farm - Again, a Zenith 5-F-134 in much worse shape.