LOCATING COMMON TROUBLES, CHECK LIST [FM Simplified (1960)]

The purpose of the following check list is to point out those components or areas in a receiver where the defect for the various types of troubles indicated is most likely to be located.

No Sound

1. Defective tube.

2. A-c line voltage not reaching the receiver. Check fuse.

3. Selenium or semiconductor rectifiers defective.

4. Defective power supply component.

5. Try signal injection, starting with stage closest to loudspeaker.

AM Reception, No FM Reception

1. Defective tube. (Check those dealing with FM only.)

2. Check AM, FM switch.

3. FM oscillator defective.

4. Measure voltages on tubes dealing with FM only.

5. Try signal injection in FM section.

FM Reception, No AM Reception

1. Defective tube. (Check those dealing with AM only.)

2. Loop antenna open.

3. Malfunctioning AM oscillator.

4. Check AM, FM switch.

5. Measure voltages on tubes dealing with AM only.

6. Try signal injection in AM section.

Weak Sound-All Signals

1. Defective tube in power supply on audio amplifiers.

2. Defective volume control.

3. Low voltage in power supply, audio amplifiers, or I.F. stage.

4. Use signal injection in audio amplifier section to locate trouble.

5. Defective loudspeaker.

Weak Sound- AM Only

1. Defective tube in AM section.

2. Defect in AM detector circuit.

3. Open loop antenna.

4. AM oscillator not functioning strongly.

5. Check AM, FM switch.

6. Misalignment in AM circuits.

7. Low voltage in AM stage.

Weak Sound- FM Only

1. Defective tube in FM section.

2. Misalignment in FM circuits.

3. Check FM antenna.

4. FM oscillator not functioning strongly.

5. Low voltage in FM stage.

6. Check AM, FM switch.

7. Defective component in output network of FM detector.

Hum-Always Present

1. Cathode-to-heater leakage in audio amplifier tube.

2. Defective filter in power supply.

3. Poor ground connection in audio amplifier circuits.

4. Leakage in multiple-section filter capacitor when one of the sections is in the audio system.

Hum-Present Only When Signal Is Being Received

1. Leakage across R.F. amplifier, oscillator, or mixer sockets.

2. Cathode-to-heater leakage in R.F. amplifier, oscillator, or mixer tube.

3. Poor ground connection in R.F. stages. (This includes R.F. amplifier, oscillator, and mixer.) Hum-Phono Operation Only

1. Poor ground connection in phono assembly or in connecting cable.

2. Poor electrical connection at phono input jack.

3. Leakage from phono motor to cartridge head in pickup.

Fuse Blows

1. Defective tube, particularly in power supply.

2. Shorted filter capacitor in power supply.

3. Defective selenium or semiconductor rectifier in power supply.

4. Short circuit across B+ line (generally a shorted bypass capacitor).

5. Shorted winding in power transformer.

6. Shorted filament in parallel-wired filament circuits.

7. Try disconnecting all B+ lines, then reconnecting them one at a time.

Defective Operation During Certain Hours Only

1. Check power line voltage during these times.

Distorted Sound

1. Defective tube.

2. Low B+ voltage.

3. Misalignment of FM detector.

4. Open filter capacitor.

5. Leaky audio coupling capacitor.

Signal Drift

1. Defective AFC circuit.

2. Defective oscillator and AFC tubes.

3. Open or shorted components in AFC line.

4. Change in component value in oscillator circuit.

Noisy Reception

1. Defective limiter.

2. Misalignment--all circuits.

3. Poor ground connections.

4. Defective bypass capacitor in audio amplifiers.

5. Dirt or grime on tuning capacitor plates.

6. Defective tube.

7. Loose connections.

8. Misalignment of FM detector circuit.

Signals Only Over Portion of Dial

1. Misalignment of R.F. circuits.

2. Defective oscillator tube.

3. Tuning capacitor plates shorting.

4. Defective oscillator component.

Tuning Dial Markings Off

1. Misalignment of R.F. circuits.

Intermittent Operation

1. Defective tube.

2. Poor ground connection.

3. Fluctuating line voltage.

4. Defective selenium or semiconductor rectifiers.

5. Defective capacitor.

6. Defective resistor.

7. Loose connection.

Motorboating

1. Open filter capacitor.

2. Open bypass capacitor.

3. Poor lead dress.

4. Poor ground connection on shield.

5. Open grid resistor.

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