Katun 4615 OPC Drum

[+ve charge]

Hi..... We have just acquired under contract a bunch of Ricoh FT4615's. Some of these machine have recently (10k copies and less) been fitted with Katun Drums. Most of the machines display an annoying tendancy to give a black background copy (the original print is visible through the background on the copy) or a copy with black lines ever so often (but not consistently). I'am thinking the problem is with the Drum Earth but because the problem is not consistent am unsure. Now I know the best option is to fit all of these machines with OEM drums but that is not an option at this point. So if any of you have any suggestions or opinion on this matter that would help me i'd be grateful and happy to try it out. thanks and have a good day.
"Sorry to be an analog in the world of digital "

[enics]

Just only to suggest it. I'm not a technician. But, I deal with Canon 3050 copier. Please, try it with the good one machines' setting same to a background image occurring machine. I want to mean setting will be on Service Mode or hardware card.