XEROX WORK CENTER 7755 BLACK SPOTS ON BLACK drum

[Dunu]

XEROX WORK CENTER 7755 BLACK SPOTS ON BLACK drum
I have some little spots over black drum of my XEROX WORK CENTER7755 Copy printer:
The problem lies with black section; it prints black spots on a print out.

When I removed the drum unit I noticed that there were a lot of spots on the surface of the drum and the drum got damaged . They weren’t the toners that formed the spots but they were peeled out coated layers of drum. (in little -little spots.) The new drum on the machine hardly prints 20o copies and it will damaged the drum with spots again.

I had lost 3 new of black drum cartridge units because of this problems (little spots)
I had changed developer unit, the problem remained the same.
I had filtered all developer to see if there is any sandy material or foreign object but I could find any thing in it .
Please can any one help me and solve my challenge.
Thank you .

Timothy Dunu

[nicks]

I don't think that anyone is home here on the forum. I've been waiting for a response to my issue. I guess that we all win some and lose some.

[exCSER]

Hi Dunu,

I don't work on that particular model, but I've been servicing high-volume machines for about thirty years now, and that sounds like the kind of problem that would occur if the charge corotron were arcing, usually caused by bad wire or inadequate (high resistance) return.

Hope this helps.

Don

[Dunu]

Dear exCSER.
Thank so much for your reply, you have elevated my spirit.
I have this kind of machine family (Xerox dc 250 ) which I do service and maintain with the same problem. I tried all best , no result and I became frustrated .
Once again thank you.
Please further explain to me how to solve the BAD WIRE OR INADEQUATE (HIGH RESISTANCE) RETURN.
Thanks for your anticipating response.

Timothy Dunu

[exCSER]

Hi Timothy,

The charge corotron (offshore machines call this the corona) wire can develop hot spots that can cause the high voltage that goes through the wire to arc to the drum, damaging the surface in the manner that you described.
The charge that is applied to the drum has to have a return path to ground or the same type of arcing can occur. The machines that I have worked on that use a drum for the photoreceptor usually have a metal plate on the inboard side which makes contact with another plate inside the machine for its return. Sometimes these plates can become contaminated and do not make a sufficient electrical connection, increasing the resistance in the circuit.
Hope this helps!

Don

[Dunu]

Dear exCSER,

Thank you so much!

let me do as you said, I will feed you with the result.


Timothy Dunu