panasonic dp 1510 white patches

[nkprl]

yes exactly the same with black lines (blade etc)

[copiman]

It could be a bias issue like it changing before it should. The top part seems ok and then it fades towards the trail edge, right? You should have somewhere around -430Vdc for bias measured on the front of the developer unit. Did you change developer? If not how many copies on developer?

If you have another laser unit you could use, I would try that. Also ensure you have a good drum ground. Have not seen drum ground issues, but would not rule it out.

[nkprl]

ok guys at last i opened the lsu and cleaned the polygon mirror, the machine came to its normal operation.
All the replies were very helpfull thanks.