How to open hp clj 3505 printer side cover - HP COLOR LASERJET CP 3505 N PRINTER

SOURCE: getting a 59.c0 error on hp clj 3505

Is the transfer unit installed correctly?Check and refit the transfer unit.

SOURCE: 59.c0 error in hp clj 3505 printer

For those users who are having a problem with the printer motor, this C level problem is referred to as 'developing disengaging motor rotation error'. Most likely, this problem points to an issue with the function of the DC controller: either it has failed or it has affected the developing disengaging assembly. The solution is quite simple and the user may fix the error in a matter of few steps.
The first step is to reconnect the J16 connectors that are used for the developing disengaging motor to the J1100 connectors that are used for the DC controller PCB (that is the printer circuit board of the DC controller). After connecting these two connectors to each other, the user must replace the developing disengaging drive assembly directly.
The final step is to replace the DC controller PCB, after which the printer is to be recalibrated. for more information....
http://www.fixya.com/support/t503092-59_c0_error_hp_color_laserjet_5550