strange problem bizhub c451

[mik77]

On each working half are good and half ago the defect. Strange thing is that the mold vertically and horizontally.
The defect does is printing pdf, jpg, than from any program.
immaging units are new and internal tests are perfect.
the machine prints 140,000
Cosa ne pensate.
Thank you in advance

[allan]

How does copies come out?
You need to rephrase that, your question is difficult to understand.
Do you know how to print half-tones in service mode?

[mik77]

excuse my English.
halftones-mode service are perfect
of a work of 10 prints, 5 or 6 the problem occurs.
As you can see from the test, the defect is in the upper part of the sheet.
Prints only black and magenta, yellow is not printed

[allan]

you say copies are ok or not?

Did you reinstall/reseat the yellow imaging unit?

[blackcat4866]

Print this. It will tell us more:

=^..^=

[allan]

Print this. It will tell is more:

=^..^=

That will work well.

[mik77]

copy is used little
imaging unit yellow new
test pattern ok
It could be the laser or the ram???

[allan]

Print blackcat's test print and post that. Without knowing if it's limited to printing or if it's happening with copies as well we can really eliminate problems.

[emujo]

Pull laser unit and clean dev/toner droppings..I think that will clean up the voids, I would replace 2nd x-fer roller as a option for the poor color transfer. A lot of internal test prints are black only, problem would not show up unless you are running color. Emujo

[mik77]

copy the problem does not occur.
It is like the machine had problems to process the data.
I'll try to replace laser, ram and controller MFP.
thanks for your advice