A. Low ink content. Should change the ribbon.
B.Wrong setting of the printer driver. Should set the printer driver into double color printing.
The broken printer head causes the problem. Should change the printer head.
A.The printer head is far away from the paper. Should adjust the regulating stem.
B.The printer head is abraded, broken or dirty. Should change the printer head or clean it.
C.The inked nylon life end. Should change the ribbon.