HP M281cdw faded print and missing print issue

[Lzep]

I have the same problem as others had noted on this printer but I have not seen it resolved anywhere.  It has to do with faded image and what is called Missing Print Issue. I saw an HP Support video on youtube which pointed out the problem, It's title was "Toner Color Cartridge Troubleshooting'.   The solution was to move the alienation tab out of the way on the missing color as seen on the printout of the supply status page.  My missing color is magenta.  In my case the alienation tab was in the correct position yet the color would not print. I tried a troubleshooting technique which allowed me to swap cartridge locations by moving the chips in the cartridge between the yellow and magenta cartridges. The magenta cartridge now prints out fine in the yellow cartridge position and the yellow cartridge does not print out in the magenta cartridge position. Seems to be no toner distributed from a cartridge when in the magenta cartridge position. There has only been 200 pages through this thing. Most of which have been trying to fix this issue.  The supplies read at 80% life left.  I found no help from the link supplied to Nicholas on that page.  I hate to toss this thing into the landfill with this low of a page count. Any  fix suggestion?

[Repairatrooper]

On the left side of the cavity where the toner cartridges sit there are 4 spring contacts that provide ground for the drums so that they can be charged properly to transfer toner. It is possible that the magenta contact is bent or broken. Use a flashlight to examine that side of the cartridge cavity and see if anything looks out of place. This is a little difficult with the cartridge caddy in place but you should be able to see.

[Lzep]

Thank you Repairatrooper for the suggestion.  I have removed the cartridges and caddy to gain access to the contacts.  The magenta contacts look similar to the other three.  There is also a contact (small spring) on the caddy at each cartridge location.  Since you pointed this out as a potential problem area, I will examine it more thoroughly tomorrow. 

I was expecting to see continuity between these four contacts on the printer side of these contacts.   Each must have its own circuit.  Depending on how the contact check turns out, I'll have to dig into that side of the printer to see if something may be obvious.  Maybe the electrical open is on the circuit board side.  

I had removed the right side cover to examine the mechanical workings.  It looks like all the wheels are spinning. 

In addition to the magenta totally missing,  the whole image is washed out.  On other printers, that problem was dirty optics in the laser scanning module.  Not sure if this printer has that? 

[Repairatrooper]

Yes this device uses a laser scanner, however if the printer is not really dirty that is less likely the problem than a contact or power issue. All 4 contacts are separate because they all are energized with different levels of power depending on amount of toner left, condition of the drum units, etc.

[Lzep]

The electrical connections looked good and nothing looked distorted or bent.  I ran a wire from the contact on the printer to the contact on the magenta cartridge just in case there was a misalignment.  No change.  

Next I took the left side cover off and removed the main board which had four spring loaded contacts which interfaced with the two rows of electrical contacts inside the printer.  I'm not sure what the upper row of contacts touch on the cartridge.  There doesn't seem to be a conductive pad in that location??  Maybe it makes contact with a carbon material??

It appears the black cartridge has one spring contact for the lower contact and one spring contact for the upper contact. 

All three lower contacts of the three color cartridges are tied together and go to one of the last two springs.  

All three upper contacts of the three color cartridges are tied together and go the the last of the springs.  

Another strange thing... all the lower cartridge contacts are electrically tied together via the cartridge caddy.  There is a metal rail which all of the cartridge springs attach to.  

Not sure what to try next.  Unfortunately sending it away for repair is not cost effective.