(1) Paper moisture;(2) the drum unit or toner damp problems;

(3) after exposure erasing drum poor, low surface potential;

(4) lack of exposure;(5) magnetic roller side down;(6) transfer voltage is low.

(1) first replace other drying of paper before printing, if the fault disappears, it indicates that the paper damp.

(2) If the print paper problem, consider the problem of the toner.

(3) If the first two are normal, the fault persists, there may be the drum charging electrode, the transfer roller electrode contacting bad or questionable cause.

(4) After the above checks are correct, if the drum toner image on the surface of normal and test sample on the toner density is not enough, then it is surely a result of low transfer electric field strength. Check the transfer charger wire (transfer roller) whether contamination or poor contact, and clean it. If the electrode wire transfer models, check the correct position of the electrode wire. If the above parts are normal, then check the transfer high-voltage generating circuit and overhaul copy paper;