Why a damper isolation transformer?

[init4fun]

Since the heater power for the majority of the tubes was grounded to the chassis on one side of it's line , connecting the damper's heater with one side grounded was said to put too much potential between the now grounded heater and the operating at much higher voltage cathode . This caused many HK shorts in damper tubes and you'll find some sets with a separate damper heater winding incorporated into the main transformer for this very reason . The aftermarket transformer was used as a repair for sets without such a separate winding that were repeatedly shorting damper tubes .