Error 061 - 001 canon ir5075

[zelotprotos]

Dear Friend....

My canon IR 5075 has 061 - 001 error (I have this error two or three times on the on the other machine )

Setting : OPTION ---> BODY ---> PO-CNT = 1 : The machine shows that error.
Setting : OPTION --> BODY --> PO - CNT = 0 : the machine has no error at all. but the copy result has dark background so I tried to set the height of the primary charge and also the transfer charge to reduce the dark background print but it always has the half black background print.
Some guy tell me that the laser is the problem.
on my first machine I have bought new laser and fix the problem.
but accidently this new problem get the same problem again: Error 061 - 001.

please give me some advice, what 's the wrong ?
What is the important thing to do when replace the laser?

thank you.

(I am sorry, wrong place, I have moved this thread to canon forum )