canon ir5870ci

[srv]

HI there,has anyone come across a problem when copying colour,background starts appearing after approx 8 copies and gets progressively worse.On removing the process unit there is a lot of toner on the drum.I have swapped the drum and transfer blades with another m/c,also the pre transfer and primary coronas but still the same.There is approx 130000 on m/c.Any ideas would be much appreciated.

[roho]

Questions: What is the colour: b/w ratio?
What kind of colour-heavy coverage, coloured text?
Any error codes in recent history- eg: E020?
This m/c was designed for a low colour ratio.
What do your pg5s' look like?