asked Mar 16, 2006 at 7:03am
Canon Canon LBP 4

Fixed my Laserjet 4m, now a question about parts

Recently, a local university threw out an otherwise fine looking laserjet 4m printer. I decided to adopt the poor guy and see if I could nurse him back to health. Skip to the last paragraph if you don't care about the narrative.

It powered up fine, and went through the self test. Then it powered up the scanner mirror. I would have thought a helicopter had crashed through my roof. On disassembly, I found that the fixed magnet around the mirror assembly had shattered. I figured I'd try a simple solution first, and I used good old cyanoacetate (super glue) to reassemble the pieces of the magnet that had been so nicely trapped in the sealed scanner assembly. It powered up, and the sound coming from the scanner was much better, but alas, I still got error 51, loss of beam detect, on printing.

I ordered a new scanner assembly, or at least the closest one I could find. I ended up getting a lot of two assemblies and dc control boards for a 4+. Since they looked similar, I figured Canon used the same scanner in both engines. Both scanners continued to give me error 51. So I came up with a novel solution, I opened the scanners, and removed the laser diode and beam sensor from the defective scanner, and installed them in one of the new units. Lo and behold, the thing worked!

So here's my question:

Are the scanner assemblies for a 4M and 4+ identical, and I just happened to be sold defective units labeled as working. OR, is there a difference between the laser generating unit and sensor on the two?
laserjet 4m scanner part number rg5-0449
laserjet 4+ and 5 is rg5-0903

hp4 is a ex engine and the 4+ and 5 is a ex2

scanners willnot swop...
by shotgun on Mar 16, 2006 at 9:10am Add comment