HP M553 No Black Print after replacing Toner

HP M553 No Black Print after replacing Toner Issue:

Originally the printers failed to print black after a toner change. When trying to replace the “pre-exposure PCA” other colors quit working as well. No image was being written to the drum.

Resolution:

For those of you who directed us towards the grounds on the toners, you hit the nail on the head. However, it was complicated. I tried to take some pics (see attached) and I will now try and explain.

- The end of each toner has a small brass square on the top which is the only source of a ground. When the toner is slid in to the machine, this brass square sits slightly below a brass “spring” in the shape of a “V”. As the front door is closed, the toners are lifted ever so slightly and press against this spring to create contact. This was brought to our attention and verified early in the game. Our springs were all in good shape and the toners being lifted to touch them.

- To replace the pre-exposure PCA, the black plastic panel holding these springs has to be removed and re-installed. When re-installing the panel, there are 3 tiny “J” hooks at the bottom that need to be pushed through the metal frame of the printer and lifted to lock them in. If these “hooks” rest on the face of the frame, they hold the plastic away from the metal just enough that the back side of the ground springs don’t touch the frame. One would have “assumed” these springs were wired on the back of the plastic to a ground, but in fact they simply rest against the frame when properly installed. When my tech first removed the plastic because black was not working and installed a new pre-exposure PCA, he put it back in such a way that the “J” hooks were on the face of the frame instead of through it and none of the springs were touching on the back and thus we lost all colors.

- So, why did the initial problem occur on multiple machines and seem to surface after a toner change? Turns out that the little “J” hook on the plastic just barely hooks the frame. When removing a toner, it is easy to “snag” (or catch on) the plastic just enough to pull the hook to the front side of the frame and prevent the back side of the grounding springs from contacting the frame. For every ground not touching, that color does not write to the drum. One, or any combination of, these grounds can be disrupted if the users carelessly remove a toner when replacing them.

Hopefully this is clear as mud