> hello!..I tested my SB220 with 4.1 volt on the > filament..witch had 500w output.when i pushed the filament > to 5 volts with external power,the output went to 1kw > plus.... > > //SM7TVJ Please, why was the voltage low so we can learn from what you found. What was the cause of the low voltage? 73, Tom W8JI