Lanier LP020c laser colour printer horizontal lines

As if the cartridge is new.and colour is printing fine.then its not faulty cartridge or faulty printer.and yes you are absolutely right that it needs proper servicing.in the printer there are lens one lens is for colour and one lens is for black.if there is dust on the lens controlling black you will get lines and patches in black prinouts.but yes if the drum is got lines on it.that it will give same lines in the printouts.also you can get the drun serviced first before getting the printer serviced.a local printer repair shop does this drum servicing.also there comes a liquid to clean drum.you can get it from printer parts store.if want to do manually.but the shop will get it checked after serving in there printer.so it will be confirmed that is it drum or faulty /dusty lens in the printer. ----------- this will help.thanks.