New installation Bizhub421

[techguy]

Just got a new bizhub421 installed. Have follow the instruction in the manual installation carefully. Notice during the tcr adjustment successfully but the result is pretty high above 90. Normally just above 40. When perform test copy the result is black background. The black background just half the paper the other half is clear. Anyone can explain why this happen on a new machine?

[minimerlin]

Remove the drum unit and make sure that the charge corona unit is fitted correctly..the grid must be the same distance from the drum all along its length. It is easy not to fit the unit correctly!