How to Repair Old-Time Radios: Intro and Article Index

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Intro to this Guide:

Don’t give up on that broken-down relic of the golden years of radio. Just a few minor repairs or easy tube replacements can give it new life. That dusty forlorn-looking old radio in the secondhand shop or in your own attic or basement was made with a care and a quality of parts that would be prohibitively expensive today but you can restore it to good-as-new condition and turn it into a valuable collectible and useful source of entertainment.

And you don’t have to be a radio expert to do it. You don’t have to have a lot of expensive equipment either. Chances are you already have the tools and supplies you need to fix most sets. In some cases a VOM—an all-purpose electrical tester that can buy at any electronics store for a few dollars and learn to use in a few minutes—will come in handy but you may not even need that.

You will need some basic information however—the kind of practical nuts-and-bolts data you’ll find in this guide. This guide is the culmination of years of experience in troubleshooting and repairing radio equipment and teaching others to do the same. It is as clear and simple and practical as I can make it. It is not a guide on radio theory because I realize that the collector is more interested in getting a worthwhile old-time radio to work than in how it works. Some theory—perhaps a brief review of what you learned in high school physics about electronic tubes—will be useful and is included. But even this can be sugarcoated. Most of the theory you will need to know is presented as a history lesson rather than an electronics lesson. I have found that this chronological approach is not only more interesting and palatable to most persons it is also more logical, sensible and meaningful. Furthermore, the information thus learned is far more likely to be retained. But again, contrary to what you have thought you do not need to know any radio theory to fix most sets. In many cases all you need to know is which tube to unplug and replace and if it is a type no longer made, what other tube can replace it. That is the kind of practical matter in which you and I are interested.

One of the problems in servicing old-time radios is in replacing defective and non-available parts with present-day items. Many of the tubes used in the old sets have not been manufactured for many years, but there are quite a few types that can be replaced with currently manufactured tubes with no wiring changes. Other obsolete tubes can be replaced with other types of the same era. To help you with these substitutions, I have included a “Mini Manual of Out-of-Date Tubes” virtually a guide within a guide which provides complete data on the old all-numbers types (00-A to 864) as well as the early “standard” types (such as the 2A5 and 6A7).

Of course, a radio set is more than just tubes so I have also provided specific practical information about checking other parts—sometimes using just your senses, such as sight, touch and smell. I have also included full particulars on replacing, repairing, substituting, and reconstructing the other parts that go to make up a radio. I have done this for just about every part except the cabinet, whose refinishing and repair is along the same lines as for an antique or collectible furniture.

If you are new to the hobby of collecting antique radios, I bid you welcome. If you are new to the rewarding work of repairing them, I wish you luck. As a collector and restorer of antique radios, you will be working to preserve a priceless piece of our technological heritage. I am proud to help.

Contents of this Guide:

1. The Pioneers and Their Creations

Tube Types—Sockets for Tubes—How Tubes are Numbered—Data and Uses of the Tube Manual—Origin of Receiver Input—Functions of a Receiver—Diode Detector—TRF Receiver—Superheterodyne Receivers

2. Understanding Schematics

Unit Terms used in Electricity—Voltages Are Differences in Potentials—Influencing Factors

3. Start Here!

A Troubleshooting Method that Never Fails—Preliminary Troubleshooting—Signal Substitution—Signal-Tracing Method—Circuit-Disturbance Method—Stage-Muting Method—Localizing Intermittent Troubles

4. Specific Circuits and Their Problems

Voltage Measurements—Resistance Measurements—Isolating Trouble in Audio Circuits—Isolating Trouble in IF Amplifiers—Isolating Trouble in RF Amplifiers—Isolating Trouble in Mixer Stages—Isolating Trouble in Converter Stages—Isolating Trouble in Detector Stages—Isolating Trouble in Power Supplies—Troubleshooting in Power Supplies—Isolating Trouble in Oscillator Stages—Localizing Trouble in Automatic Volume Control Circuits

5. Testing Tubes and Other Parts

Tube Checking by Substitution—Checking Series Filaments—Testing Parts—Checking Resistors—Testing Coils and Transformers—Checking Capacitors

6. A Handy Guide to Common Problems

Troubleshooting a Weak Receiver—Troubleshooting a Distorted Receiver—Troubleshooting an Intermittent Receiver—Troubleshooting a Receiver for Hum—Troubleshooting a Noisy Receiver—Troubleshooting a Receiver that Squeals or Motorboats—Universal Troubleshooting Chart

7. Repairing Radio Parts

Repairs in General—Installing Small Replacement Parts—Repair and Replacement of Variable Capacitors—Repairing and Cleaning Electrical Contacts—Tube Socket Repair—Cord and Cable Repairs—Repairing Shielded Cables and Wires—Repairing Transformer Windings—Tube Reactivation—Rewinding AF Coils and Chokes—Repairing Switches—Repairing Fixed Variable Resistors

8. Substituting for Unavailable Parts

Tube Substitution—Data and Uses of the Tube Manual—Use of the Mini-Manual of Old/Time Tubes—Substitute Filament and Plate Transformers—Substitute for Ballast or Line Cord Resistor—Loudspeaker—Substitute Resistors and Capacitors—Mini-Manual of Old-Time Tubes

9. From the Author’s Bag of Tricks

Capacitor as Test Instrument—Using a Power Transformer with Half of the High-Voltage Winding Open

10. Receiver Tune Up for Top Performance

Basic Concepts of Alignment—Alignment Precautions—AM Receiver Alignment—Location of Trimmers—I-F Alignment—Oscillator, Mixer Input and RF Alignment—Aligning Receivers with More than One Tuning Range

11. Advanced Radio Theory

Tube Functions—Electron-Tube Radio Receivers—TRF Receivers—Superheterodyne Receivers

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Updated: Tuesday, 2015-12-22 6:14 PST