Poor print quality on Konica Minolta C454e

[U12runzn]

Hi I'm having issues when I print , the page background has black shades that get worse as the machine prints . As if the prints are dirty .
Steps taken in attempt to resolve the problem -
Changed entire drum unit Corona wire included
Changed developer
Change transfer belt
Everything was changed with original parts
Cleaned printhead laser glass
Technician went into service menu and calibrated a few times
It seems as if the first printed less dirty and as the machine prints more copies the black shadow increases. It prints all colours but the black shadows print over .
What else could possibly be wrong with this machine
The technician thinks the HV needs replacing .
I'm not sure if this is related to the issue but the last toner inserted into the machine was depleting very quickly while printing however it was printing perfect
Screenshot_20220117_031202.jpgScreenshot_20220117_031202.jpg

[Synthohol]

lemme ask you, were entire brand new OEM units replaced or simply rebuilt?
i ask because you said developer not developer unit which suggests only the powder.
you also mentioned including the corona wire, if an OEM unit were replaced that wouldnt be a detail i would need to mention.
if this is the case try new units from KM, unless you have a front side board you can swap from another machine?

[Max]

Go to service mode and print out C Y M K test sheets. Line them up and if white lines line up then it will be the belt. Waste belt relay pipe not blocked? If not, developer gap blade contaminated with clumps of toner preventing uniform brush. Oem/compatible toner? Take out laser unit and clean glass by hand as magic wand doesn't always work. Compatible drums don't always work. Possibly transfer roller but in my experience unlikely nor HV board.

[U12runzn]

Go to service mode and print out C Y M K test sheets. Line them up and if white lines line up then it will be the belt. Waste belt relay pipe not blocked? If not, developer gap blade contaminated with clumps of toner preventing uniform brush. Oem/compatible toner? Take out laser unit and clean glass by hand as magic wand doesn't always work. Compatible drums don't always work. Possibly transfer roller but in my experience unlikely nor HV board.

Thanks your post was very helpful. Problem sorted

[U12runzn]

lemme ask you, were entire brand new OEM units replaced or simply rebuilt?
i ask because you said developer not developer unit which suggests only the powder.
you also mentioned including the corona wire, if an OEM unit were replaced that wouldnt be a detail i would need to mention.
if this is the case try new units from KM, unless you have a front side board you can swap from another machine?

Issue with the laser unit . Thanks for your feedback