The 3581 is a 200 watt triode made for the Fischer Company of Chicago for use in diathermy equipment. The first example was made by Taylor Tubes and appears to be a re-branded 822. Later 3581 tubes made by Taylor were taller (9.62") and had a different envelope. United also re-branded HV-27 as 3581s for Fischer.
Length = 9.13" Diameter = 2.50"
Max voltage = 2500
Max current = 300 ma
Fil voltage = 10
Fil current = 4 amps GOTO INDEX