Wireless Workshop

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Wireless Workshop

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Radios sourced by AC power are electrical appliances. General electrical safety information for appliances is widely available and is beyond the scope of this discussion.

Some special considerations, however, need to be given to safely enjoying an old radio

Radios built before the era of modern electrical appliance safety standards can pose hazards to their users. Design techniques and materials in common use when an old radio was built can lead to possible electrical shock and exposure to toxic materials. Many older radios require an external antenna fitted with a lightning arrestor and physical isolation from overhead power lines.



Radios that plug into a wall power socket almost always have potentially lethal power present inside the chassis. They should only be serviced by a person experienced in working safely with exposed high voltage sources.



Line-powered radios which do not have a power transformer, sometimes called AC/DC sets, frequently have one side of the ac power line directly connected to the radio chassis, or through a capacitor to the chassis. If the capacitor fails shorted, the result is the same as a direct power line connection to the radio chassis. If the radio has its original non-polarized power plug, a 50/50 chance exists of having the chassis connected to the "hot" side of the power line when the set is plugged in. If the user touches the chassis or any metal part connected to the chassis while also making a contact with electrical ground, a potentially fatal shock will occur.


Radios that employ a power transformer can still shock their users. Power line bypass capacitors failing shorted, or electrical leakage from the power transformer primary to the chassis, can also lead to a "hot-chassis" shock as described above.



Old radios themselves cannot be made to conform to modern electrical safety standards. Several ways do exist, however, to connect an old radio to ac power with relative safety.

The least expensive approach is to install a polarized plug on the power cord of the radio. If a polarized plug is properly wired to the radio, and ifthe ac power receptacle that it is plugged into is properly wired, then the "hot" side of the power line cannot connect to the chassis of the radio. The two "ifs" make this a fairly unreliable approach. Polarized power plugs were not original equipment on old radios; the use of a polarized power plug is also objected to by many purists as not authentic.

The use of a GFCI (Ground Fault Current Interrupter) is another way of preventing a lethal "hot chassis" shock. This device, now installed in many home outlets, will break the electrical circuit when it senses a dangerous stray current flow to ground. GFCI units are of moderate cost, and are easy to use with old radios. They require no rewiring of the radio.

Possibly the best protection against "hot chassis" shock is the use of an isolation transformer between the power receptacle and the radio. The isolation transformer provides excellent protection against "hot chassis" shock. It is the obvious choice of protection in service labs (including ours). A significant drawback is the cost, which may total over one hundred dollars, depending on the wattage required.

Wireless Workshop specifies that the radios it restores be connected to AC power through a GFCI or isolation transformer.


Lead, in the form of the solder that makes wiring connections, is present in all old radios. Lead vapor from soldering can pose a serious hazard while working on a radio. Warning information provided with solder and soldering tools must be strictly followed.

Some radio chassis and hardware were plated with Cadmium. Metal salts formed as the Cadmium corrodes are frequently yellow or yellow-green. These salts are highly toxic, and should be carefully passivated or professionally removed if present.

Asbestos is sometimes found in insulation, especially heat insulation in small radios. If asbestos is present, Federal and State environmental regulations are to be followed.


Any radio that requires an outside antenna needs to have the antenna installed with a lightning arrestor. Attention to preventing contact between the antenna and overhead power lines is also critical to having a safe antenna.

Looking for a place to have that nice old radio restored?  That's what we've been in the business of doing since 1992.

Wireless Workshop
We fix old radios


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