The amplifier is the heart pump of any audio system. It takes a small signal from a source such as a DVD player, turntable, mixer, etc. and amplifies it to a voltage that can be used to drive your speaker system.
Common problems associated with amplifiers are:
Dust, Dust, and More Dust
Amplifiers of any size produce heat. This heat needs to be removed to prevent damage to the sensitive components. To accomplish this, amps are either convection cooled (vented) or forced air-cooled (internal fan).
Fan forced amplifiers are constantly sucking in dust that builds up around transistors. Convection cooled amps are better at dust rejection but over the years dust can settle in around output stages. This dust build-up prevents heat from escaping. This is the biggest reason for amplifier failure.
Control knobs on an amplifier can develop problems. The most common symptoms include ‘scratching’ sounds, dead areas while turning or sliding controls (audio drops out in certain areas), level jumping – where the sound ‘jumps’ to another level without slowly fading. These problems are usually caused by small dust particles finding their way into the potentiometers casing and settling on the contacts. This is rectified by cleaning the casing of each control pot, and then re-lubricating it.
Other problems are caused by older potentiometers developing ‘worn’ areas. Component replacement is the only fix in this case.
Severe damage to output sections can arise when the amplifier is turned up too loud (usually the kids’ fault!), or briefly shorting the speaker leads with the amplifier powered on. This type of repair is the most expensive and obtaining parts can take a long time. It is possible to prevent damage by having the amp regularly serviced. We recommend that your Hi-Fi amplifiers are serviced every two years while pro models should be serviced once a year.
Other preventative measures include turning the amp off when moving speakers, keeping the top of the unit clean with a dry cloth, this ensures that there is adequate air movement around the amp.
Hiss and Older Amplifiers
Over time, amplifiers can start to produce a higher than normal ‘hiss’. This is usually caused by faulty or old filter capacitors. These capacitors come in many different types.
Vintage valve amplifiers and early transistor amps used a paper type of capacitor. These suffer from ‘leakage’, short, or open circuit problems. Modern aluminum types are better.
Replacement of the filter capacitors can produce amazing results.
See the Electronic Repair page for more details.