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Rebuilding Antique Collectible Vacuum Tube Radios Page 2

OddMix.com - Radio Technology Note - RTN0801 - Karl Nagy

The most important step is to do a thorough visual scan on the newly found radio. If a camera is handy, it helps, but not absolutely necessary to snap a few photographs from all sides, before removing anything. If the set was battery operated which is not very likely as those sets are much more rare, the work will be a bit more complicated, since a set of batteries - Picture 1. - required to test the radio eventually.
Picture 1. High Voltage Battery Anode B+ [3 KB]
Picture 1. High Voltage Battery Anode B+

In an ordinary line powered set, before anything else, do a real careful inspection, especially of the ancient electrical cord. There is a good chance the cord will not be up to its job, because of some insulation problem, so inspect it over and over. If it still look serviceable you may begin to inspect the radio itself.

It should be dry, and without telltale signs of liquid damage. If all is well, wipe it carefully and re-inspect. Pay close attention to the cardboard cover on the back. Usually that piece of board is full of valuable information. It may have the name of the set, its maker, time, the type of receiver and what kind of vacuum tubes are in it.

Now that all is inspected and in fine order refrain from plugging it in and start using it. Not that it can't be done, I have done it myself and gotten lucky a few times, but better to hold your horses a bit longer.
Picture 2. Old Radio Chassis Top View [8 KB]
Picture 2. Old Radio Chassis Top View

The next and important step is to carefully remove the back cover. The backside of that cover needs to be inspected, as it is often has the actual schematic diagram of the set pasted on it. Other times it depicts just the block diagram. Either way it may contain valuable important information may be needed to complete the revitalization of the long dormant receiver.

Once is decided that nothing further can be gained from the back panel, time to give the chassis a very thorough visual Picture 2. Initially, take inventory of the vacuum tubes. All sockets should have a tube in them. If the tubes have a metallic shield, remove them, on by one. The tube itself should have a deep black color that is like mirror on top and some clear part on the sides. If a tube shows white or light gray on top, it has lost vacuum, usually by either a broken tip, or through a hairline crack in its bottom part between or near its pins.


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