A New Approach to Series Heater Strings for Television

The presence of voltage surges in series heater strings represents a major source of tube failures. Tubes supplied by various tube manufacturers behave differently in the heater string. A method of tube evaluation outside the heater string enables prediction of surge conditions in the string. Surge-free operation can be readily obtained by tube selection. This selection does not provide for trouble-free operation in the event of field tube replacement. It is necessary to establish industry standardization of heater characteristics to eliminate all trouble.