Black stain shadow from the same image print

Ghosting appears often because of bad toner. If cartridges have been refilled, they have wrong toner in them. If drum has worn out it will usually tell you. All parts for this machine cost too much. If toner is not the problem, probably best to get a new machine rather than pay to get it fixed. Brothers are cheaper to run.

According to the service manual for problems with light print image, the cause can be the Developers or High Voltage Power Supply (HVPS). Other possible causes are given as: Developer roller is stained when the toner or developer cartridge is almost consumed. Ambient temperature is below 10 degrees Centigrade. Bad contacts with the HVPS or abnormal output from the HVPS. To replace the Developers you would need to purchase a replacement Imaging Kit CLP-R300A. Any problems in the HVPS would require a factory repair.

This is usually due to a dirty imaging drum roller (green roller below toner). Remove the toner / drum assembly, then separate the two. Now slowly rotate the imaging drum roller by hand using the gear on the side of the cartridge (Try not to not touch the drum roller with your hand, as oils from your skin may cause further problems + toner is nasty) Look for toner splotches to the left and right on the drum roller as you turn it. If you see any you can clean them off with a damp paper towel. Then reassemble the printer and hold the continue button down until you hear the printer start then release it; this will print a test page.. Hopefully that will take care of the issue. Also while you got the assembly out of the printer you can clean the glass print-head lens using a clean, dry, and lint free cloth. The print head lense is located within the recessed area in the top of the printer.

- I have seen that happen to a bunch of those printers and that is usually all it is. Let me know if that takes care of it.

Picture of Drum + Print Head lense for a (1720 / 1720DN).
Link to Dell manual about drum & print head.

(Full link below)

(http://www.support.dell.com/support/edocs/systems/prn1720/en/1720_en/en/d0e4183.html#replacing-the-imaging-drum)

I had replaced the fuser - no improvement. I removed the fuser, imaging unit & transfer roller. CAREFULLY using a vacuum cleaner I cleaned all units and the internals of the printer, rotating the roller on the imaging unit to clean all parts. (Warning Place Imaging unit on paper as toner escapes) After a few test prints the page cleared and duplicate ghosting cleared.

Check the fuser roller if it still has faint prints on the roller then your getting a shadow image in your prints,. Could be a bad fuser roller replace it

Shadow images may caused by several things :
1. Deformed rubber of the cleaning blade,
2. Drum aging,
3. Upper heater roller aging.

The mfr. & model don't seem right; Dell does have a 5100 but the LJ designation is copyrighted by HP who has a LaserJet 5100.
The rotating drum that transfers the image to paper is smaller in circumference than the paper is long; this accounts for the shadow and the streaks come from the drum no longer being properly discharged and cleaned for the next pass.
I think you need a new drum cartridge and whether Dell or HP made it, you should be able to buy a drum cartridge here:
Precision Roller 
I used them for years while in business and they are great to work with.

check the two levers with an envelope on each, to the left and right of the fusing unit, should be pressed down and not rise up.

Reset your Toners and Imaging units for Bizhub and CF series.
http://www.chipreset.eu

Usually the Drum and the cleaning blade must be replaced together. Hope you done this already, if not replace the cleaning blade.
The problem can be in the fuser unit. Pleace check and replace the Hot roller, thermistor and HR strippers as a set and also the pressure roller bushings.

call brother and tell them that the drum is shadowing and needs to be replaced or you can look in your area for a cartridge World and pay them to remanufacture that drum and If you are going to be printing check you really need to find a printer that has micr toner it has more metal ion the toner which makes it burn hotter.The toner that you are using may possibly be able to be lifted and info on the check could be [email protected]