October 2007 Featured Technical Article

What Good is Color Without Black?

If you’ve been working on color laser printers for a while, you’ve probably noticed they are a little more complicated to trouble-shoot than your standard monochrome printer. In a monochrome printer, if you have an imaging problem you typically start by swapping out the toner cartridge. Swapping cartridges changes multiple parts that create the image and odds are you will eliminate the problem when you do this. Even if it doesn’t fix the image problem, the next steps are squarely in one area. Not so in a color printer where you have four color toner cartridges. This means you need to isolate which color is causing the problem, or which imaging area of the printer is causing it.

 With the Color LaserJet 3700, 3500 and 3550 series, there is a new common failure that is really confusing to trouble-shoot. The typical symptoms are a blank page when printing text, or no black on a color page - with no error code (Figures 1 and 2). You may notice in the figure with missing color there is some black. Some pages will have some black like you see here, while others will have none all together.

Figure1

Figure2

 With our focus clearly on the black toner, what could cause this type of image to be printed? It could be a bad toner cartridge but that would make the article too short. No that’s not it! It could be a problem related to the black toner cartridge slot such as a blocked laser beam, bad high voltage contact(s), seating of the toner cartridge, or the drive. We can isolate between a cartridge problem verses a cartridge slot problem by running the Disable Cartridge Check in the Diagnostics Menu. This test allows the service tech to move toner cartridges around without causing an error code. The logic is then to move the black toner cartridge to another slot such as the yellow, and move the yellow toner cartridge to the black slot. Running this test as described would show black toner on the page where yellow belongs, but a complete lack of yellow. Since this occurred, we have determined the problem is with the black cartridge slot.