by Bob Putnak, ©2010.
Of all the subjects that I have discussed, I receive the most inquiries about my HP Officejet “scanner system failure” repair article. That article also fondly mentions the old-school Laserjet’s, and I had several inquiries about repairing them. These old dinosaurs are still useful to any small business that prints traditional business text documents or for printing schoolwork. So here is an article about how I have repaired and refurbished these Laserjet 4L and 4P printers in the past (not so much anymore!) Do not attempt if you are not qualified to perform such repairs or do not want to risk further damage or inability to reassemble your printer. The basic concept is similar with other models not shown here, although disassembly will be somewhat different.
These printers were built like a tank and page-feed problems are the most common complaint. A general overhaul will take care of most of these issues. In summary: the printer is torn down, thoroughly cleaned with compressed air (including the 4 optical sensors on the mainboard), rubber rollers are treated with rubber rejuvenator, the sticky-stuff is cleaned off of the relay coil, the relay coil arm is wrapped once with thin black electrical tape. If you have a dead printer, you will also inspect the power supply fuses, although a blown fuse is usually the symptom of a real power supply defect.