LaseJet M553 Missing Black, (Or Color), No Error Code When Printing.

[SHThompson]

I have inherited an M553 from another Tech, he had already replaced the DC Controller, Laser/Scanner and HVPS, (High Voltage Power Supply).

I disconnected the Flat Cable that connects the Formatter to the DC Controller and did an Engine Test, same symptom, I reconnected the cable and ran a Half Self Test.

After doing the Half Self Test I determined that I had an image formation issue.

Following some thinking and verification that all the mechanical parts were working  I decided that the most likely point of failure would be the Ground Supplied to the OPC Drum, which on this machine is on the front of the toner cartridge and is easily accesible.

I removed the front door and closed the inner black toner door and then used a meter to check from the Frame to the copper contact on each cartridge, the colors all checked as connected to Frame Ground, the Black was NOT connected.

So I "Hot Wired" the Black by connecting a Meter Lead the the Frame and holding the other end on the copper contact on the black cartridge. The black then printed fine.

We then removed the black plastic inner cover that the Ground Contacts are installed in, this required removal of the Top Cover since there is an Interconnect Board mounted on the black plastic part and you have to remove the board before the black plastic inner cover.

The contacts are very simple, they are just a Torsion Spring on a Plastic Frame, one arm pushes against the printer frame and the other against the contact on the Toner Cartridge.

We swapped the Black Spring with the Cyan Spring and cleaned the Frame with alcohol, (99% wipe).

After reassembling just far enough to test we found we now only printed Yellow and now had three bad Ground Connections.

We tried again and got Yellow, Magenta and intermittent Black.

I'm currently on hold with HP Support trying to determine if the contacts/mounting frame are orderable.