How Do You Locate A Microphonic Tube In An Amplifier?
One of the most common failures in vacuum tubes is the development of microphonic properties. This occurs when the tube begins to act as an antenna and introduce stray sounds into the circuit, which is obviously a problem for amplifiers. Microphonic vacuum tubes not only make the amplifier noisy but also may be a precursor to amplifier damaging electronic failures. Luckily, locating microphonic vacuum tubes is easy. Remove the access panel and inspect area around vacuum tubes. If tubes have individual metal covers remove them (they usually twist off). If any tube is broken or cracked, it must be replaced. If the area around any tube looks as if it has been melted or burned, there may be an electrical problem and the unit should be referred to a qualified technician. Connect the amplifier to a speaker if one is not built into the unit. Turn the amplifier’s main power switch on, but do not turn on the standby switch if unit is equipped with one. Give the unit three to five minutes to hea
