A Guide to Basic Valve Amplifier Repair

The other name of the valve amplifier is tube amplifier. It is a type of electronic amplifier that uses vacuum tubes. Hence, it increases the power of a signal. Some of the applications using valve amplifiers include guitar amplifiers and satellite transponders. However, when we talk about satellite transponders, one can use them in direct TV, GPS, high-quality stereo amplifiers, and military applications (such as radar). Apart from that, it also includes very high-power radio and UHF television transmitters, etc. 

Many companies provide valve amplifier repair services. It includes servicing to restoration, from repairs to rebuilds, etc. But, every company must understand the technology of this application. The valve amplification has existed for over 80 years. In short, this technology came in the 1930s and 1940s. Most modern valve amplifiers come from this technology. According to most people's opinion, valve amplifiers sound much better than transistors. Therefore, people prefer to use them. 

Pros and Cons of Valve Amplifier:

When people listen to the valve amplifier sound, they are blown away by its quality and experience. In older times, everyone loved tube amplifiers, but everything started to change rapidly as technology advanced. The time came when for amplifiers, people used transistors for their production. One of the major highlights is that they do not require any repair or service like a tube amplifier. However, many true music lovers returned to the old tube amplifier because of its sound quality and other benefits over the newer transistor amplifiers.

The following are the pros and cons of a valve amplifier.

Advantages:

• The harmonic distortion of valve amplifiers is tremendous, making the sound more attractive.

• One can get the best quality at all levels. 

• It provides softer clipping.

• They are suitable for high voltage circuits.

• Valve amplifiers are electrically very robust. Thus, they can tolerate overloads for minutes.

Disadvantages:

• It requires a cathode heater, significant heat loss, and energy use.

• If we compare it to solid-state amplifiers, they require higher voltages for the anodes.

• Solid-state devices have smaller tubes, but valve amplifiers have larger ones. 

• Due to various failure mechanisms like heat, breakage, cathode poisoning, or internal short-circuits.  

• And, they have lousy linearity, especially regarding modest feedback factors.

A Guide to Repair Valve Amplifier:

Some people think that valves are not reliable. On the contrary, valve amplifiers are more accurate and dependable than transistor amplifiers. Most of the large airports still run valve-driven radar systems. If we talk about different countries, the USA is the biggest importer of valves for their radar sets. Similarly, the Russian defense utility depends on the valve system. All of the fighter planes and ships have valves. The primary reason for using valves is that it is rare as they will not damage during a conflict because of their magnetic pulses and interference spikes. However, they can affect other parts if they fail, so timely repair is necessary. 

1. Valve Matching:

Valve amplifier repair will last longer if you do not mix new and old valves. First of all, use decent quality valves in the first place and make sure they are operating correctly. Thus, they will function properly for many years to come. 

2. Biasing Method:

Any valve must work correctly, must give it correct voltages. Biasing is a method that keeps the valves in a stable condition within their operating limits. However, there are two methods of biasing. The first one is Grid and the second one is Cathode. Grid biasing applies a negative voltage to its control grid and forces the valve to come into a stable position. Cathode biasing is another method that allows the valve itself to bias automatically by choosing resistor values carefully. However, both ways need care; otherwise, they will become difficult to repair. 

How to Repair Valve Amplifier:

All valve amplifiers repairs go through the same procedure of repairing. An unserviced amplifier will need the power supply high tension capacitors replaced. Similarly, one also needs to replace all the coupling and bypass capacitors. The resistors must be accurate, and if there is any overheating issue, it needs repair. 

The chassis needs cleaning from inside and out. Apart from that, the control switches, controls, connectors, etc., also need cleaning. After checking everything, it is best to check the amplifier's output power and distortion level. Amplifiers will benefit from reducing distortion by altering one or two-component values. Many amplifiers also benefit from updating using modern components or changing the circuit. To make a difference, one should also replace poor speaker terminals with decent and proper ones. 

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