Bizhub C550 Image gradiation key are lost.

[ReoNeo]

Hello... Can someone please help me with this following problem.
I got one C550 where the image gradiation key are lost from expert adj. and rep tech mode.
And i hope someone can tell us how we can get it visible again.
Thank you.

[Bizhub]

Go into service mode, then image adjustment and then turn off DEV BIAS CHOICE.
Now you should be able to grad adjust your machine.

[ReoNeo]

Thanks for all help... Its work again...

[levino]

I got two 6500 and one 6501 mcs,regularly the customer will complaint that the gradation is not correct.Can any one explain me whats gradation and how can adjust . it will help me a lot.my experiance is less in the mcs

thanks in advance