C451 printing only in yellow

[seniortech]

I have a very sick C451 (180K). During customer run they got the message to reload bypass, after that every single print/copy came out in yellow until machine was switched off, as things stand now If you run stabiliser the transfer belt is completely yellow, however you can just about see the coloured registration marks underneath the yellow. The machine will quickly contaminate belt and 2nd transfer roller with yellow toner.

If you run graduation test prints, blocks of color are printed out with what seems to be a tinge of black dev on the edge of the sheet (feels rough to touch). if you print a yellow test page yellow is almost completely missing. if you copy a test chart of the glass there is no yellow in the copy at all again but there are two unequal bars of yellow running down each side (A3) of the sheet with random yellow spots and patches in the body of the sheet. all of the colours are washed out and can barely be seen.

I have replaced yellow imaging unit, transfer belt unit, 2nd transfer roller, HV1 and HV2 problem is still there.

I could try the various control boards, but to me it still looks to me very much like a HV problem. has anyone seen this problem or anything like it or give me any idea what this may be?

Thanks

[mojorolla]

Sounds like the yellow DV unit. I didn't see DV as one of the things replaced.

[seniortech]

C451 has image unit, comprising Drum/Dev/and Charging unit

[seniortech]

Turned our to be laser unit

[mrwho]

Great. Thanks for coming back to provide us with your feedback. Reps to you.