Loose connection in the choke
Loose core
Loose winding turns
Loose cover screw
Tube lamp will begin to flicker
Tube lamp will go out immediately
Tube will operate normally
Tube will begin to hum very much
low voltage and limit current
low voltage and increase current
high voltage and limit current
high voltage and increase current
surge voltage and limit current
surge voltage and increase current
will continue to glow
will get fused
will not glow
will glow intermittently