Collectibles-General (Antiques)/Zenith farm radio
I own an old Zenith farm radio and would like to know how I might get it to work. I bought a 6 volt battery but I can't get it to play. Can you help me figure it out? Is there a tube or electrical component malfunctioning? Also, what is this radio's age? Thanks so much!
That is a nice piece you have there. It is a 4 tube vibrator powered receiver. I assume it is intended to operate off 6 volts DC from a battery.
Usually the contact points of the vibrator are oxidized to the point it can no longer function. When it is functioning it makes a slight buzz. The vibrator is located on the rear of the chassis on the right side as you face the back of it. It is in a fairly large can and plugs in. What the vibrator does is make the DC from the battery into a form of alternating current which is fed to the power transformer immediately adjacent to the vibrator. The transformer steps the 6 volt power up to 150 to 250 volts. Another set of contacts in the vibrator converts this AC voltage back to DC which is used by the tubes. Vibrators are available from Antique Electronics Supply in Tempe, Arizona (www.tubesandmore.com) and Radio Daze (www.radiodaze.com). These are solid state vibrators and do not have the problem of oxidation like the mechanical ones do. Whether you can get one with a set of rectifying contacts to change the AC back to DC from them, I do not know. Also, you may have to change the socket to accomodate their unit. Ordinary rectifying diodes rated 1000 piv or more could be used. I prefer to use 2 in series in each leg to assure against voltage spike damage.
It looks like the radio still uses the original electrolytic capacitor. This is probably dried out to the point it will no longer function. This will cause a very loud buzz in the loud speaker if it is not replaced.
The buffer capacitor(s) should also be replaced. Be sure you read their capacitence in mfd off the old units and get exactly the same value as before. Also, be sure the voltage rating is at least as high as the originals.
I have been successful at prying apart the vibrator and sandpapering the contacts to make it work again. Once you have the vibrating contact working, there is some tendency for it to clean itself as it runs.
Radios with the tubes used in yours were made in the 1930 to 1935 time frame, so you have one of the early 6 volt farm radios.
I have a set of Ryders manuals and could email you a copy of the service literature for the radio if you send me the model number of your set. Here is my email address: email@example.com
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