Bizhub c451-uneven top of the copy/printout

[mik]

CAN SOMEONE HELP ME WITH THIS PROBLEM ON THE KM BIZHUB C451 THE TOP OF THE COPY/PRINTOUT IS MUCH LIGHTER THEN THE REST 3/4 OF THE PRINT,ON BW COPY OR COLOR IS THE SAME PROBLEM,BLACK LINES,TEXT OR COLOR PRINTOUTS IS MUCH LIGHTER IN THE TOP OF THE PAPER,IT IS THE SAME WHEN YOU COPY OR PRINT.BLACK,MAGENTA AND CYAN IMAGE UNITS ARE REPLACED,NEW.I TRAY WITH CHANGING THE TRANSFER ROLER AND TRASFER BELT,THE PROBLEM STAYS,THAN I CLEAN LED ROWS UNDER THE IMAGE UNITS AND MIRORS UNDER THE LED ROWS,SEVERAL TIMES I DO THE ADJUSTMENTS GRADUATION,SATURATION ETC,AND IMAGE STABILIZATION AND GUESS-NOTHING,PRINTOUS AR LITLLEBIT BETTER BUT STILL THE TOP OF THE COPY STAYS LIGHTER THEN THE REST.BEFORE ALL THIS I CLEANED OPTICS AND INSIDE MACHNE,CHECK ALL CONTACTS ON THE TRANSFER ROLLER AND CLEAN CAHRGE WIRES,ON ALL IMAGE UNITS,BUT THE PROBLEM STAYS.I WISH YOU ALL BETTER LUCK WITH BIZHUB C451,MINE IS COUNTED ABOUT 621000 COPIES,130000 COLOR,I CHANGED ONE FUSER UNIT,ONE TRANSFER ROLLER AND TRANSFER BELT,AND SEVERAL IMAGE UNITS,YELOW IU-S LASTS SHORTER THEN SHULOD BE,THE REST IS OK TILL NOW.

[Jantje]

Screaming

please stop SCREAMING!!!!!!, this is really unreadable, and I don't even try to do that.

[8050]

Heh, he sounds desperate hence the yelling. Ok, On your gradation test patterns, YMCK - 65/75% density, which colors are showing this fadeness on the top of the prints?

[harry2007]

laser unit

bizhub c451 do not have LED rows. It works with laser .
Laser unit (P/H assy) for this macnine and also for c550, c650 it.s a new model but not so good.
So, your problems are located in this laser unit -try to clean mirrors,glass frames, lens...but no more chance...
more simple is to change this unit with new one- it's easy to change it .
and important:
no smoking and no dust in that area .

[mik]

first of all i am sorry because may bad english,but i hope who want he will understand what i want to say,when i said led rows i think about a cleaning glass under iu units. I take out yesterday ph unit and open it, cleaned all mirrors,glass frames and rest, put it all together and the printouts is the same. Both bw and color is lighter on the top. But when i open ph unit i did not seen so much dirt inside, mirrors, glass filters were been very clean,with no visible dust or some kind of dirt on their surface. The machine is instaled before 12 months. The test pattern shows lighter printout on the top also and everything that i print or copy on that c451, bw or color shows much lighter text or pics on the top.thank you all for your understanding.

[mik]

i am sorry for may screaming i did non now how difficult is to read that kind of text,so i bold up past messages.Every color shows fadeness on a test pattern.

[mik]

ORIGINAL MESSAGE,from the top of the pagewithout so much screaming, i hope sorry all
CAN SOMEONE HELP ME WITH THIS PROBLEM ON THE KM BIZHUB C451THE TOP OF THE COPY/PRINTOUT IS MUCH LIGHTER THEN THE REST 3/4 OF THE PRINT,ON BW COPY OR COLOR IS THE SAME PROBLEM,BLACK LINES,TEXT OR COLOR PRINTOUTS IS MUCH LIGHTER IN THE TOP OF THE PAPER,IT IS THE SAME WHEN YOU COPY OR PRINT.BLACK,MAGENTA AND CYAN IMAGE UNITS ARE REPLACED,NEW.I TRAY WITH CHANGING THE TRANSFER ROLLER AND TRANSFER BELT,THE PROBLEM STAYS,THAN I CLEAN LED ROWS UNDER THE IMAGE UNITS AND MIRRORS UNDER THE LED ROWS,SEVERAL TIMES I DO THE ADJUSTMENTS GRADUATION,SATURATION ETC,AND IMAGE STABILIZATION AND GUESS-NOTHING,PRINTOUTS ARE LITLLEBIT BETTER BUT STILL THE TOP OF THE COPY STAYS LIGHTER THEN THE REST.BEFORE ALL THIS I CLEANED OPTICS AND INSIDE MACHINE,CHECK ALL CONTACTS ON THE TRANSFER ROLLER AND CLEAN CHARGE WIRES,ON ALL IMAGE UNITS,BUT THE PROBLEM STAYS.I WISH YOU ALL BETTER LUCK WITH BIZHUB C451,MINE IS COUNTED ABOUT 621000 COPIES,130000 COLOR,I CHANGED ONE FUSER UNIT,ONE TRANSFER ROLLER AND TRANSFER BELT,AND SEVERAL IMAGE UNITS,YELLOW IU-S LASTS SHORTER THEN SHOULD BE,THE REST IS OK TILL NOW.

[mik]

tomorrow i will try to open laser unit,which is inside PH unit of bizuhb c451,and clean what i can clean inside,because i do not have new right now,did someone do something similar with this type of machine or this type of the ph unit?

[8050]

I've heard that a mirror or lens can go off position causing some wierd CQ issues. Guess if you're still having this problem after replacing alot of parts it doesn't hurt to check.

[mik]

you mean mirrors or lenses inside ph unit,becaouse all optics ws checked several times?which i should i check?when i opened ph unit for frst time on that machine,last time all mirrors seems to be tight and in position i will try to open laser today to check if is dirty and i will check position of his lenses.Thanks for your advice.

[Albonline]

replace the ph unit!

[mik]

i clean ph unit today,and copy is much,much better,light part in the top of the copy is disappear,both bw and color,but when i opened laser unit,on the back of ph unit i was very,very careful all parts and the filters across laser is very sensitive to scratches even from the cleaning cloth,especially two plastic lensses before polygon mirror,they are soft as a cheese,and i really dont get it how so much dirt can get inside that unit,when i have some other cheap laser copier such as 1611/162/163/211,which is working for years in worst enviroment then this c451,and i have no problem with their laser units,such as bizhub 162,work in dirty storage count 960 000 copies,and evrything wor like dream!probably too much moving parts and not so tight housing.Thank you all.