A/C alignment adjustment locations:
----------------------------------

While there are many variations on the exact locations of each of the A/C
head alignment adjustments, the following description is for one of the most
common layouts.  See the appropriate sections elsewhere in this chapter for
the adjustment procedures for the A/C head.

* A/C mechanical tracking.  This is a conical nut on a small shaft fastened to
  the transport base.  It is wide on top and tapers down below.  A slot across
  the top allows the nut to be turned and thus raised or lowered.  Its angled
  side presses against a projection on the A/C assembly base plate.  Thus
  raising or lowering the nut moves the A/C head assembly from side-to-side.

  - When raised (counterclockwise), the A/C head assembly moves away from the
    video heads increasing the delay between the video and sound.

  - When lowered (clockwise), the A/C head assembly moves toward the video
    heads decreasing the delay between the video and sound.

  You may need a special screwdriver with a cutout in the middle of its blade
  (or modify one of your own) to easily adjust this nut.
 
* A/C head height - A hexagonal nut on a large shaft behind the A/C head.  This
  moves the entire A/C head assembly up and down.  A spring underneath provides
  both the upwards pressure to keep the A/C head assembly against this nut and
  torque to keep it against the conical A/C mechanical tracking nut.

* A/C head tilt - A Philips screw is directly behind the A/C head on the plate 
  that the head sits on.  This adjusts the A/C head forward and backward (with
  respect to the tape).
 
* A/C head azimuth - Another Philips screw is to the right or left of the head
  on the same plate just mentioned. It probably has (had) some red (or other
  color) paint on it to lock its position.  This adjusts the A/C head azimuth
  angle (side-to-side) with respect to the tape.

* A/C head plate pressure.  A third Phillips screw (on the opposite side of
  the A/C head from the azimuth screw) with a spring under it.  This should
  just be left alone as its only function is to provide downward pressure to
  keep the A/C head assembly in place as determined by the tilt and azimuth
  screws and a pivot point underneath near the front.  However, if it seems
  loose, tighten it a few turns clockwise.  This should not affect any of
  the other settings.

Adjustment of A/C head - problems with tracking or sound (linear audio):
-----------------------------------------------------------------------

If the problems happened suddenly, it is probably not a misadjusted
audio/control head but some other mechanical fault - eliminate
this possibility before considering A/C head adjustments.

The following will attempt to get your mechanical settings back to something
approaching normal even if the audio/control head was tweaked:

I assume that you have cleaned it and replaced any dead rubber parts.

I also assume that someone (we won't name anyone) has tweaked just about
every mechanical adjustment.

I would adjust the audio/control (A/C) head as best you can (don't touch this
unless you know it was messed up by someone):

* Play a tape that you know was recorded on a good machine.  It may be easier
  to start with a tape recorded in SP mode since this is less critical.
  Once the basic alignment is complete, go back and fine tune with a tape
  recorded in EP.

* Adjust the A/C tilt as vertical as you can by eye.   If necessary, fine
  tune it for most stable tape movement - the tape should be at the same angle
  moving over takeup roller guide, A/C head, and adjacent fixed I guide.

* Adjust the A/C height for loudest sound.  At each end of the range of this
  adjustment, you will lose tracking/sync and tape speed may fluctuate (in
  addition to the sound becoming weak).

* Adjust the A/C azimith for best treble (high frequency) sound.  This is
  a precise adjustment - a 1/16 of a turn is significant.  There will be
  a very small range over which the sounds will be clear and natural.
  A tape with music is best for making this adjustment.

* With electronic tracking control centered, adjust A/C mechanical tracking
  (usually, a conical nut that moves the entire A/C assembly) until
  you get the least snow (if you have a picture at this point).
  Satisfactory tracking may be obtained at several positions of this control.
  However, only one will produce current video-audio sync.  For the others,
  the words and the picture will be off by some multiple of 1/30th of second.

* You may need to go back and touch up some of these again.

There can still be other problems in the tape path including the height
and angle of the roller guides and the height of the impedance roller
assembly (on the left before or after the full erase head.)