[CQ] C6501 - Banding in all colours

[Eugene74]

Hi there everyone,

Hope somebody could assist me in this regard. I have a C6501 with 311K copies on. PM has been done a 100K ago, and a month ago (10K copies) I replaced the coronas asthey where causing light lines in copy direction. Now suddenly I get light patches (Banding) over all colours and if you print halftones over 130 (Test pattern 1) it is not noticable, anything below that value you can see the banding. I did replace drums and transfer belt, to see if it resolves the problem, but with no luck.

I have included samples (CMYK is been printed on setting 110, on test pattern 1, and the last page that looks blank is yellow been printed on setting 80. And you can hardly see any toner coverage.)

I hope anybody could help me whit this.

Many thanks
Eugene

C6501 Banding.pdf

[cns]

Re: C6501 - Banding in all colours

Hi Eugene , lyk my Knysna hou jou besig. Dis een van die moeilikste probleme op daardie masjiene . Ons het destyds dieselfde probleemhier in George gehad. Is die banding in CD of FD ?GroeteCN

[jrf]

Re: C6501 - Banding in all colours

Take a careful look at all drive gears in fuser unit.
I had a very similar call on a c6501 which had one tooth broken on one of the fuser gears

[27842]

Re: C6501 - Banding in all colours

If you have a spare Dev unit i would try it, any color and see if prints clear up . Also some of the Drums a have been getting lately show the same symtoms as your prints. The prints at 110 do not look so bad mabey magenta and black could be a problem but at that low density you will see more inperfections.
Good luck.

[Eugene74]

Re: C6501 - Banding in all colours

Thanks for all the input. I'm going to have look at the problem today again, and will try all suggestions. CN yes they have me by the short hair, and I'm running around. Those copies defects are in CD, what were the problem you previously had at the George customer if I may ask? How is business there by your side?

Regards
Eugene

[RRodgers]

Re: C6501 - Banding in all colours

Clean the second transfer roller. (the one next to the fuser)

[Eugene74]

Re: C6501 - Banding in all colours

Hi all,

I have been to the machine, I did replace drums, Dev Tanks, All the transfer rollers, I've checked the fuser, the fuser belt and fuser rollers were replaced, but no broken gears on the drive of the fuser unit. At this stage I'm clueless and don't know were to look anymore, the problem is still there. Any more suggestions, would be appreciated.

Many Thanks
Eugene

[Albonline]

Re: C6501 - Banding in all colours

can you exchange the first transfer unit into another unit? or get another one to try in the problem unit?

[dljorg]

Re: C6501 - Banding in all colours

Running test pattern 1 the machine does not actually use a print screen. Suggest you try test pattern 53 in both Line 1 and Dot 1 screens and see if you get the same type marks. The sample you attached (very good by the way) looks like bad dev units but I reject that as you have changed them.

Any chance the customer's paper is maybe damp? You should try paper from a sealed package and maybe bring some of your own to the party. Make sure the machine is set for the weight and type paper you are actually using.

If there is a problem with the transfer belt not moving smoothly and causing these uneven densities you should be able to tell by checking the automatic Color Registration adjustment. First be sure that the Belt Line Speed adjustment really is at 205.7mm or darn close and the setting is between -5 and -35. Then do the Color Registration adjustment and write down the three numbers for sub scan. Do the adjustment again, maybe even 3 times. If the drums and transfer belt are moving consistently and smoothly the sub scan numbers in the Color Registration adjustment should not change more than +/- 0.5. If they do change more than 0.5 then you should review how the transfer belt assembly is put together. Grim experience says transfer belt unit assembly is the one thing on the C6500 series that gets done incorrectly most often. Get in the service manual and check all the assembly details.

Someone above correctly mentioned the second transfer roller. The springy electrical contact on the front of the roller should be on a smooth end surface NOT on the lathe indent which guarantees a bad transfer current at the roller.

[HoonBoy]

Re: C6501 - Banding in all colours

From the TSG:

[Probable cause]
a) If blank area exists in the halftone area, the transfer current concentrates to the halftone
where toner is attached. Consequently, the transfer ratio increase at the halftone then
density increases.
b) If solid area exists in the halftone area, the transfer current concentrate to the solid part
where the more toner is attached. Consequently, the transfer ratio decreases at thehalftone area and density decreases.
[Solution]
By reducing the 1st transfer current, the current concentration degree can be reduced and thedifference of the density is improved.
[Utility Counter] =>[03 Machine Admin. Setting] => [01System Setting] => [05 ExpertAdjustment] => [06 Process Adjustment] => [01 Front & Back Density]
Reduce the 1st transfer current from yellow to black by step by step (decrement by 1 step) andfind the best condition.
The banding cannot be eliminated completely but can be improved.
[COLOR=rgb(100.000000%, 0.000000%, 0.000000%)]CAUTION: If the 1st transfer current is decreased too much by [01 Front & Back Density]adjustment, the white spot may appear. Please mind it and check the image carefullywhen performing the adjustment. [/COLOR]

[RRodgers]

Re: C6501 - Banding in all colours

Clean the second transfer roller. (the one next to the fuser)

Try what th is guy suggests, also clean the laser slit glass for all colors as well.

[940021]

Re: C6501 - Banding in all colours

Try This One...

[inutelkamo]

Re: C6501 - Banding in all colours

Hi,

is this problem solve?

having same problem..

thnx