C6500 horizontal lines in print

Hi. I have the horizontal lines that the red arrows show in the attachment. I changed the four drum units because I thought that it was the drum units but I didn't get any better result. What do you think that is causing this? The problem I have is that I need import any spare part to my country because there's no distributor to buy locally. So I need some advice because I need to buy it and then wait for a while to get it. I want to order the spare parts that I most probably need. Or maybe it can be some adjustment issue? I can give 19,000 dpi resolution of a section of the print if some one thinks it would help to determine possible causes. I sent the image in mid size because it won't upload in higher resolution.

Thank you.