Hi Friends! Please am having this big challenge: Black small dot spots all over the black drum of Xerox dc250 and Xerox work center7755 I had changed more than 4black drum unit for each of them, each drum doesn’t copy 400 copies before the new drums got damaged. I was advice to change the following parts/Consumables for 2machines(dc250and 7775) Black Developer unit, Developer and PSHV-S4 board and PSHV-S5C board The problem persisted and no solution Please can any one help with solution and shall be appreciated. Timothy Dunu