S
SaladFingers
Take the tube out the fleurescent for now then it wont affect the dimmer
He or she has already taken the starter out, but the ballast will still be connected in the loop, so ought to be disconnected.
What loop
Its a switchstart fitting, the live will go to the choke then will only go to one unused hole of the lampholder with the lamp out
There may be a capacitor across the supply but i think unlikely to bother the dimmer
The ballast is still connected in the circuit and will be trying to do something, much like a transformer with no lamp. Plus not all ballasts like to be run with no tube.