RISK OF SHOCK
Electronic amplifiers are powered from the AC mains distribution. High AC voltages and AC currents are present in the chassis and present a risk of shock to the user. Lethal power levels are available from the mains. Keep hands clear of mains wiring.
Vacuum tube electronic circuits operate at high voltages. High DC voltages are derived from high AC voltages and both represent a significant shock hazard. Injury and death may result from contact with these voltages. Keep hands clear of secondary wiring and high-voltage circuitry.
RISK OF SHOCK FROM UNPOWERED EQUIPMENT
Capacitors can store electric charge for very long time periods. Electronic equipment that is unplugged from the mains and has not been powered for days can still hold enough charge to cause injury or death. Carefully discharge capacitors using recommended techniques (not shorting) prior to working on the unit.
Electronic equipment creates heat during operation. Proper air circulation and/or fan cooling will remove this heat from the unit. Do not obstruct ventilation or otherwise impede heat removal. Do not defeat protection circuitry or any devices such as fuse, current limiters, temperature monitors, fan servo circuits, power reduction circuits, in prebuilt circuits or in circuitry fashioned from schematics shown in this text.
Electronic devices and chassis containing them can become hot to the touch. Avoid contact of skin with these surfaces as severe injury can result. Tube envelopes can be 250°C at their hottest point. Soldering iron temperatures approach 450°C.
SOLDER FUME & MATERIALS HAZARD
Solder used to secure electronic devices contains tin and lead. Solder for electronics use also includes a resin core to clean the connection while soldering. The resin and solder create fumes that may be hazardous to health if inhaled. Exhale gently while soldering. A low-speed fan to extract the fumes is recommended. Ventilation to outside air is preferred. Surface residue on electronic components may be hazardous to health. Wash hands after working with electronic components.
The reader must exercise due care in heeding safety advice presented by the author when the reader constructs circuits inspired by those presented. Work space should be uncluttered, nonflammable and nonconductive. Safety and power limiting test bench devices should be utilized when testing and repairing electronic equipment. Never leave equipment unattended if powered.