C6501 Strange banding on yellow

[_scoekt]

I've got a strange banding showing up on yellow only. Picture attached of yellow, then swapped cyan dev unit, and finally cyan. I swapped the cyan dev unit with yellow and the same banding so I'm pretty sure it's not the dev unit. Also swapped drums, coronas, transfer belt and checked/cleaned HV connections for 1st transfer/dev/coronas with no change :(. Any suggestions?

[Herrmann]

You have swapped all except the laser units, so the next step imho would be to swap yellow against cyan or magenta laser unit

[_scoekt]

Just swapped write unit Y with M and no change :( Presently looking at HV units and will swap with another machine to test if cleaning/reconnecting contacts has no changes.

[_scoekt]

I swapped HV/2 but no change. I think it has to be connected to dev bias, or could it be developer motor?

[Herrmann]

Did you change only the transfer belt, or the whole unit? what about the transfer rollers (those beneath the belt), did you interchange them too? due to your work, it is clear, that the error must be in the yellow area, the only thing that comes in my mind, that you have not touched until now, are the erasing leds, maybe they are faulty and leads to drum memory.

[_scoekt]

Yes, I actually swapped the EL with another early on. Also checked the voltage /w 51-0 and read just like the others (22v I think). The belt was a entire new unit from a working machine so I'm pretty confident it isn't the 1st transfer roller in the belt. I thought possibly it was 1st transfer charge from HV/2, but no luck with that. I now am looking at swapping HV/1 and checking the dev motor and possible it isn't turning at proper speed.

[Mick01]

Hi,
This could be a screening issue.
Try printing in Line screen (line 1 or 2) and see if the issue gets better.
Line screen is usually the best for solid flat colour in this model.
Note, you will have to re-calibrate the controller for the new screen otherwise your colour will look different.
Hope this helps.

[tulintron]

Hi,
This could be a screening issue.
Try printing in Line screen (line 1 or 2) and see if the issue gets better.
Line screen is usually the best for solid flat colour in this model.
Note, you will have to re-calibrate the controller for the new screen otherwise your colour will look different.
Hope this helps.


Exact. The above test eliminates certain cases.
From when the problem occurred?
Would not it be mechanical?
Something obstructing the developer unit into position?


Own experience: Problems bizarre, trivial causes.

[_scoekt]

So after tearing the machine down and swapping HV1/HV2 with known working boards the problem persisted. Cleaned contacts several times. Messed with AC Bias/1st transfer charge with some improvement in banding overall, but still the odd bands persisted. As Mick indicated line 1 is screening shows less banding on yellow. The only problem is another c6500 we have can print same test pattern with nice results on dot 1, this is why I thought must be mechanical. So I began an extensive search and discovered KM added a dipsw 3-0 in firmware G00-40 for a "New yellow screen" on Dot 1. Setting it back to 0 solved all the problems. I've cut and pasted the excerpt from the release notes.


1) Dot1 Screen has been changed. DipSW 3-0=1: New yellow screen
0: Conventional screen (default for C6500/6500P)
* Default of C6501/C6501P =1.