Joe Churma - Hardware Technician
A customer brought in an HP Color LaserJet 5550 printer to Terminal to be repaired. It had been in an environment that had concrete dust in the air and was making a hideous grinding noise.
The problem turned out to be all three Color Drum Drive Assemblies being worn, with the Cyan being the worst with a 200T gear also being worn. All three Color Drum Drive Assemblies had their Motor Drive Gears worn away. The concrete dust acted like a grinding compound. The service manual for the HP CLJ 5550 does not have a procedure for replacing the Drum Drive Assemblies.
I used my years of experience of working on laser printers, which goes back to when they first came out back in the day - when the Image Drums were driven by chains like a bike chain. I worked out the complicated procedure to replace all three Color Drum Drive Assemblies and replaced them. I also did an extensive PM to the HP CLJ 5550, cleaning all of the concrete dust. This turned out to be a expensive shop call, but the customer was very happy with the result and ended up with a great running color laser printer for printing his Cad Cam print jobs on for around one quarter of the cost of a new printer.