Patent ID: 7602578

Claim:
A servo writer, which writes a servo signal on a servo band of a magnetic tape, comprising a magnetic tape driving system in which a magnetic tape supplied from a supply reel is taken up by a take-up reel to drive the magnetic tape; a DC erasing head which is slidably in contact with said driving tape and which DC-magnetizes said servo band and has an azimuth relative to said servo band; and a servo signal writing head provided on a downstream of said DC erasing head in the driving direction of the magnetic tape, which is slidably in contact with said driving tape and which magnetizes the servo band by a magnetizing force having a component with a reverse magnetizing force relative to the magnetizing force of the DC erasing head in the lengthwise direction of the magnetic tape; wherein the DC erasing head has an azimuth relative to said servo band so as to exert a smaller magnetic force in the running direction of the magnetic tape under a certain current input than a magnetic force obtained when the DC erasing head is transversally positioned relative to the running direction of the magnetic tape under the same current input.