I have just tested my sons K8026 with a 40W light bulb. The dimming range seems very small. The light bulb is already bright when switched on, and only gets fractionally brighter.
Is this correct?
If on 230 Volts: hope you did not mount R2? On 230 Volts minimal lamp/load is 60 Watts.
I’m using 230V and yes - I mounted everything - including R2.
Ah yes - missed that part in the manual! R2 removed, and all is well!
Ok, solved quickly 
EXCEPT that on the 3rd attempt to use it, something has blown 
Not very good news… your lamp got broke and meanwhile made a short circuit? Check fuse and triac in that case.