bizhub pro c5501 heavy toner on non-op side of sheet

[NeroInk]

Hello, and thank you to anyone who reads this. I'm an offset pressman kinda new to the digital world these past few years with a small shop in Chicago. We have used machines we try to keep up with through university of youtube etc (KM bizhubpro 5501c and 654e). They have been pretty good to us but have taken a beating lately.

We were having image issues in the magenta unit on our 5501c. I replaced drums, developer assembly + fresh dev, coronas and cleaned up the unit best I could. On the non-op side a heavy band of toner prints a semisolid all the way down the sheet lengthwise. It is bad on thin paper and gets much better, although with poor image quality, on heavier stock. There is also a bit of "picture framing" at the tail end of the sheet.

Having trouble with the drum peculiarity adjust, throwing code 2812. Also having a bit of issue with gamma adjustments. Voltage for the M drum was way up in the 200s, ordered a HV detecting assembly.

Not sure what else to do. I'm pretty good with following directions and searching message boards but have limited digital press knowledge base to work from. Anything helps!

RedToning2.jpg RedToning1.jpg

[Ziggy]

Did you replace the entire drum units or just the drums? If you replaced the entire drum units it looks like you have a defective magenta drum unit. to test you could swap the yellow and magenta drum to see if the copy quality follows the drum

[NeroInk]

Replaced both Drum Unit and Developer Unit. Swapped drums, coronas, entire developing unit, and still have excess toner only on magenta. Always on non-op side before and after change. Thick paper seems to work OK but still has picture framing on end of sheet. I swapped out the transfer rollers on image transfer belt as well with Y to see if there is an issue there, no luck.

[Ziggy]

So you moved the magenta drum and the problem stayed in the magenta? I would only move the magenta drum first to see if it moves with the drum. if you have a defective drum unit the if the color changed. Example if you move the drum from the magenta to the yellow and the yellow down to where the magenta was and you still have magenta on edge and yellow looks good then drum is ok.
If swap developer units around for testing make sure to tape over the toner add ports so you don't contaminate the developer with wrong color toner. Test target 53 at 128 density is a good one to check the color channels. have one color at 128 density and all others at zero and run only one print especially if you move the developer units around

[NeroInk]

Yes we moved drum units from Y to M, as well as installing a brand new developer unit. I hope the HVassembly is the culprit because there aren't any other imaging parts that I am aware of. Since it is better with thicker paper I wonder if it is the transfer belt unit, maybe a bad bearing or roller, but inspection and swapping has not yielded any results.

[Ziggy]

You can tape over the toner add hole on both dev units and swap yellow and magenta. Run a test target 58 at 128 density of yellow and all other density set to zero. Then run test target 58 at 128 density of magenta and all others density set to zero.
the yellow test will come out magenta and the magenta test will come out yellow. If when you test the yellow you have a dirty magenta like before then you might have a bad developer unit. However if it looks good then you ruled out the developer unit.
If you run a magenta test with developer units swapped and it comes out bad then you know that something in the magenta channel is bad.