Applying Power to an Antique Radio

Question: I just acquired an antique radio. I don’t know if it works or not. Can I plug it in and turn it on?

Answer: NO!

Never plug in and turn on an old, unrestored radio until it has been thoroughly checked for signs of trouble. This includes, but is not necessary limited to:

• Replacing the electrolytic (filter) condensers.
• Examining the underside of the chassis, paying close attention to the bottom of the power transformer. Look for any signs of a waxy substance leaking from the transformer. If you see it, the transformer has overheated at some time and may no longer function properly (if at all).
• Testing the tubes, especially the rectifier tube (a Type 80 in most older Philco sets).

After replacing the electrolytics and checking the tubes, power may now be applied. It is a good idea to bring it up slowly with a Variac (a variable power transformer in which the set being tested is plugged into, and which has a knob which sets the output voltage of the unit, usually from 0 to 150 volts). If you found any waxy substances leaking from the power transformer, the use of a Variac is strongly recommended.

Once you approach 90 volts or so on the Variac, you should be hearing something through the speaker. If you wish, you may hook up a wire antenna to the antenna terminal of the set. You might receive some stations. However, since the set probably has capacitors inside it which are as old as the set itself, don’t be surprised if you receive nothing.

If the set’s power transformer was leaking wax, it may start to make a frying sound as the Variac is turned up, or the set may start to hum loudly, even though you replaced the set’s electrolytic condensers (you did replace them, right?). If this occurs, turn the Variac off and unplug the set – the power transformer is bad. If no frying sounds are heard, and all seems well, hook up an antenna and turn the Variac on up to 90 and check for reception as above.

Even if the set works after this is done, don’t be surprised if the quality of reception rapidly degrades, a sign that the old paper capacitors are failing. Replace them. Yes, all of the paper capacitors. These (along with the electrolyic condensers) can be obtained from many sources, several of which are listed in the Resources section.

Question: I’m in a hurry. What can happen if I just go ahead, plug my old set in and turn it on?

The electrolytic condensers could be shorted, which will cause your power transformer (if one is used) to fail.

The same can be said of the tubes, notably the rectifier.

If the radio is a 1939-1942 Philco model, which uses wiring with rubber insulation, the rubber may have fallen off many of the wires, creating a potentially hazardous condition if the right bare wires were to touch each other!

Side note: How can wires be touching each other?

If the radio had been knocked about; if someone has pulled the chassis out and played around, not aware of what they were doing; if mice had previously lived there; ad nauseum. It is always better to be safe.