Originally posted by SLYTubes are able to conduct small currents because the heater 'boils off' some electrons from the Cathode. These charge carriers are not available if the tube is still cold.
... So what happens if the stand-by is turned on before the power switch ?
The Standby switch connects the high-voltage section of the power supply to the plate circuits of the tubes. If this connection is in place when the Power switch is first turned on, there is a large voltage difference between the plate and the cathode of each tube. With the cathode still cold, there is a high probability of arcing between these electrodes, causing physical damage (called sputtering) to the structure. This literally tears chunks of metal out of the electrodes! :eek:
