Connect your oscilloscope's "X" and "Y" inputs to the balanced 1/4 inch outputs of the outer tracks of the tape machine. For example, tracks 1 and 8 for an 8 track machine.
Locate the azimuth setting screw on the tape machine's playback head. If the azimuth screw is not clearly labeled, consult your machine's owner's manual for it's location.
Load a wound test tape reel on the left spindle of your machine, so that the reel will unwind counterclockwise. Thread the tape through the heads according to your machine's owner's manual. Wind the tape counterclockwise onto an empty take-up reel, placed on the left side spindle. Make 2 or 3 winds so that the tape is secure to the reel hub.
Play a 1KHz tone on your test tape and, using a screwdriver, adjust the azimuth setting screw until the two waveforms on your oscilloscope's display synchronize as closely as possible.
Play an 8KHz tone on your test tape and repeat the adjustment process. Repeat again while playing a 16KHz tone to make your setting as precise as possible.