Erase head positioning method

In a video tape recording and reproducing apparatus utilizing a rotary scanner having first and second pairs of record heads, first and second pairs of playback heads, and first and second generally opposed erase heads, each capable of erasing two adjacent tracks of a magnetic tape and having a dimension in a direction perpendicular to the path of said tracks to provide a slight overlap onto the tracks adjacent the two adjacent tracks, a method for determining the alignment of the erase heads relative to the record head, said method comprising:

• inserting into said apparatus a pre-recorded magnetic tape having a plurality of adjacent tracks recorded thereon in pairs;
• scanning said tape;
• energizing said first erase head momentarily and periodically for erasing portions of information from adjacent ones of said tracks;
• thereafter energizing said second erase head momentarily and periodically for erasing portions of information from the next two successive ones of said tracks with said erase heads being energized on a given scan on a non-overlapping basis while leaving recorded information on said tape between successive energizations of said first and second erase heads;
• playing back a channel of the thus erased tracks, said channel including first one track followed by the next non-adjacent track;
• and
• analyzing the playback waveform envelope to determine the percentage drop in the waveform caused by the overlap of the erase heads into adjacent tracks outside the channel.

In a video tape recording and reproducing apparatus utilizing a rotary scanner having first and second pairs of record heads, first and second pairs of playback heads, and first and second generally opposed erase heads, each capable of erasing two adjacent tracks of a magnetic tape and having a dimension in a direction perpendicular to the path of said tracks to provide a slight overlap onto the tracks adjacent the two adjacent tracks, a method for determining the alignment of the erase heads relative to the record head, said method comprising:

• inserting into said apparatus a pre-recorded magnetic tape having a plurality of adjacent tracks recorded thereon in pairs;
• scanning said tape;
• energizing said first and second erase heads momentarily, successively and periodically for erasing portions of information from adjacent ones of said tracks while leaving portions of recorded information therebetween;
• playing back a channel of the thus erased tracks, said channel including first one track followed by the next non-adjacent track;
• and
• analyzing the playback waveform envelope to determine the percentage drop in the waveform caused by the overlap of the erase heads into adjacent tracks outside the channel, which drop is indicative of erase head alignment.