Yamaha Cr 620 Problems

The Yamaha CR-620: a beautiful, well-built receiver from the late 1970s that brings warm, detailed sound to any listening room. But like any piece of vintage audio equipment, the CR-620 isn't immune to developing issues over time. Understanding these common problems, and knowing how to address them, is crucial for keeping your CR-620 singing for years to come.

The Silence is Deafening: No Output Troubles

One of the most frustrating problems with any amplifier, including the CR-620, is a complete lack of output. You power it on, the lights come on, but no sound emerges from the speakers. Several factors can contribute to this unwelcome silence.

Blown Fuses: Always the first place to check! Fuses are designed to protect the receiver from overcurrent situations. A blown fuse indicates a potential problem, but replacing it might be a quick fix. Never replace a fuse with one of a higher amperage rating. This could lead to serious damage to the receiver. Locate the fuse(s) (usually on the rear panel or inside near the power transformer), inspect for a broken filament, and replace with an identical fuse. If the new fuse blows immediately, there's a deeper issue.
Speaker Switch Issues: The speaker selector switch (A, B, A+B, Off) can become corroded or dirty over time, leading to intermittent or complete signal loss. Try cleaning the switch with DeoxIT D5 contact cleaner. Spray a small amount into the switch mechanism while rotating it back and forth several times. Let it dry completely before powering on the receiver.
Protection Circuit Activation: The CR-620 has a protection circuit designed to prevent damage to the amplifier and speakers in case of a fault. If the protection circuit is triggered, it will cut off the output. This could be due to a shorted speaker wire, a faulty output transistor, or other internal issues. If the protection light is illuminated, do not continue using the receiver. It needs professional attention.
Faulty Output Transistors: These are the workhorses of the amplifier, responsible for delivering power to the speakers. If one or more output transistors fail, you'll likely experience a complete loss of output on one or both channels. Testing output transistors requires a multimeter and some knowledge of electronics. If you're not comfortable working with live circuits, it's best to consult a qualified technician.
Power Supply Problems: The power supply provides the necessary voltages for all the circuits in the receiver. If it's failing, it can cause a variety of problems, including no output. Testing the power supply requires a multimeter and knowledge of electronics. Again, proceed with caution and consider professional help if you're not experienced.

One Channel's Gone Quiet: Channel Imbalance Problems

Another common issue is a significant imbalance in volume between the left and right channels, or the complete loss of one channel altogether. This can be particularly annoying when listening to stereo recordings.

Dirty Controls: This is the most frequent culprit. The volume pot, balance control, and other potentiometers can accumulate dust and oxidation over time, leading to scratchy sounds, intermittent signal loss, or complete channel dropouts. Thorough cleaning with DeoxIT D5 is essential. Spray a small amount into the potentiometer opening while rotating it back and forth repeatedly. Work the control through its full range of motion to help remove the grime. Let it dry completely before powering on the receiver.
Speaker Wiring Issues: Double-check your speaker connections. A loose or corroded connection can cause a weak or intermittent signal. Make sure the wires are securely attached to both the receiver and the speakers. If you're using bare wire connections, inspect the ends for corrosion and re-strip the wires if necessary.
Internal Component Failure: Resistors, capacitors, and transistors can fail over time, leading to channel imbalance or complete channel loss. This requires troubleshooting with a multimeter and a schematic diagram. It's usually best left to a qualified technician.
Input Selector Switch Issues: Similar to the speaker selector switch, the input selector switch (Phono, Aux, Tuner, etc.) can become dirty or corroded. Try cleaning it with DeoxIT D5 as described above. Select each input several times after spraying to help clean the contacts.

Scratchy Sounds and Crackling: Noise and Distortion Issues

Unwanted noises like scratching, crackling, and hum can significantly detract from the listening experience. Identifying the source of the noise is the first step to fixing it.

Dirty Controls (Again!): As mentioned earlier, dirty potentiometers are a major source of noise. Cleaning with DeoxIT D5 is almost always the first step in troubleshooting noise problems.
Grounding Issues: A ground loop can cause a persistent hum. Make sure all your components are properly grounded. Try using a cheater plug (which removes the ground connection) on one component at a time to see if it eliminates the hum. Use caution when using cheater plugs, as they can compromise safety. A better solution is to use a ground loop isolator.
Old Capacitors: Electrolytic capacitors dry out over time, leading to increased noise and distortion. Replacing old capacitors (recapping) is a common restoration technique for vintage audio equipment. This is a complex task that requires soldering skills and knowledge of electronics.
Faulty Transistors: Noisy transistors can also contribute to unwanted sounds. Identifying and replacing noisy transistors requires specialized equipment and knowledge.
Antenna Issues: If you're experiencing noise only when using the tuner, the problem might be with your antenna. Make sure the antenna is properly connected and positioned for optimal reception.

That Annoying Hum: Power Supply Woes

A persistent hum, especially when the volume is turned down, often points to issues within the power supply.

Dried Out Filter Capacitors: Large electrolytic capacitors in the power supply filter out ripple voltage. As they age, they lose their capacitance, leading to increased ripple and a noticeable hum. Replacing these capacitors is a common part of recapping a vintage receiver.
Diode Failure: Diodes in the power supply rectify the AC voltage to DC. If a diode fails, it can introduce noise into the power supply.
Grounding Issues (Revisited): As mentioned before, grounding problems can also cause hum. Ensure proper grounding throughout the system.

The Tuner's Gone Deaf: FM/AM Reception Problems

If the tuner section of your CR-620 isn't picking up stations as well as it used to, or is producing distorted audio, there are several potential causes.

Antenna Problems: The most common cause of poor tuner reception is an inadequate antenna. Try a different antenna, or reposition your existing antenna for better signal strength. For FM, a dipole antenna is often sufficient. For AM, the internal loop antenna can be rotated for best reception.
Dirty Tuning Capacitor: The variable capacitor used for tuning can accumulate dust and oxidation, leading to poor contact and inaccurate tuning. Cleaning the tuning capacitor requires specialized techniques and cleaners. Be extremely careful when cleaning the tuning capacitor, as it is delicate and easily damaged. Compressed air can be used to blow out dust, but avoid using liquid cleaners unless you are experienced.
Alignment Issues: The tuner section requires precise alignment to function optimally. Over time, components can drift out of alignment, leading to reduced sensitivity and selectivity. Tuner alignment requires specialized equipment and knowledge.
Component Failure: Like other circuits, the tuner section can suffer from component failure. This requires troubleshooting with a schematic diagram and specialized equipment.

Lights Out!: Display Lamp Problems

The CR-620's illuminated dial and meters are part of its charm. If the lamps are burned out, it can detract from the overall aesthetic.

Burned Out Lamps: The most common cause of lamp failure is simply old age. The CR-620 uses incandescent lamps, which have a limited lifespan. Replacing the lamps is a relatively straightforward task, but requires soldering skills. Be sure to use lamps with the correct voltage and current rating.
Loose Connections: Check the lamp sockets for loose connections. Corrosion can also build up on the lamp contacts.
Power Supply Issues: In rare cases, a problem with the power supply can cause the lamps to fail.

Frequently Asked Questions

Why does my CR-620 smell like burning? Stop using it immediately! A burning smell indicates a serious problem, such as overheating components or insulation breakdown. Have it inspected by a qualified technician.
How often should I clean the controls on my CR-620? It depends on the environment, but a good rule of thumb is to clean them every 1-2 years, or whenever you notice scratchy sounds or intermittent signal loss.
Can I use any type of speaker with my CR-620? The CR-620 is designed for speakers with an impedance of 8 ohms. Using speakers with a significantly lower impedance can overload the amplifier and damage it.
Where can I find a service manual for the CR-620? Service manuals are often available online from sites like HiFi Engine. You will need to create a free account to download it.
How much is my Yamaha CR-620 worth? The value of a CR-620 depends on its condition and functionality. Fully restored units in excellent condition can fetch a premium price.

Conclusion

The Yamaha CR-620 is a fantastic receiver, but like all vintage electronics, it requires maintenance and occasional repairs. Understanding these common problems and taking preventative measures will help keep your CR-620 sounding its best for years to come; if you're not comfortable performing repairs yourself, don't hesitate to seek professional help.