Nakamichi 481 Service Manual - page 5
2. PRINCIPLE OF OPERATION
2.1. Mechanisms
2.1.1. Headblock
Refer to Fig. 2.1.1 Headblock.
Nakamichi 481 Headblock provides more stabilized tape
travel.
Accuracy of tape travel is one of the most essential
factors for a device to optimize its performance.
Inaccurate tape travel will therefore induce deterioration
exemplified by the following:
(a) vibration will be given to tape travel, as a result of
which flutter and modulation noise will become in
creased
(b) insufficient tape-to-head contact will result in level
drops
(c) tape skew will become greater and frequency re-
sponse will become decreased
Needless to say, constant tape travel must consist of
smooth drive mechanism, as well as of the fact that tape,
heads and tape guide are placed in the most appropriate
positions.
N481 Playback Head and Record Head, they are both
made small in size so that the both heads are assembled
in a space of the conventional Record/Playback Head.
Erase Head is located at the place where the Record
Head is located in the N-700II/1000II.
Both Playback Head and Record Head are assembled on
the Head Mount Base. Take-up Tape Guide and Supply
Tape Guide are fixed to the Take-up Pressure Roller Arm
and Supply Pressure Roller Arm, respectively. Erase
Head is placed on the Head Base. All these can be
separately adjusted.
Record Head is placed slightly backward, approximately
0.15 mm away from the Playback Head. Record Head is
placed approximately 3° inclined leftward. Shape of the
Heads and its location have been carefully studied to
bring about smoother contact of tape with the Heads. Pad
Lifter is affixed to the Playback Head so as not to let Tape
Pad touch the Head to give more stabilized tape travel,
making it free from the influence of the Tape Pad within
the Cassette Tape. Thus the trouble of changes in
azimuth can now be avoided at changing of cassette tape
if only the Record Head azimuth is properly adjusted in
advance.
The Fig. 2.1.2 shows trackings of each head against a
tape of the N-481, wherein the figure shows ideal
locations at the time of designing, thus the tracking in
actual use will vary more or less, depending upon the
tape width, etc.
(1) Adjustment of Tape Guide Height
Tape Guide of the N-481 is assembled into the Take-up
and Supply Pressure Roller Assemblies. With a spring in
the stud of Mechanism Chassis Ass’y, Pressure Roller
Ass’y is tightly affixed with Tape Guide Adjustment Nut.
The Adjustment Nut is placed on a spring through Pres
sure Roller Arm, and therefore by either tightening or
loosening, height adjustment of the Tape Guide will
become possible.
(2) Playback Head Height Adjustment and Azimuth
Alignment
Azimuth and height of Playback Head can be made in
dependently and adjustment may be done separately
without affecting others. In order to adjust the tilt of
Playback Head backwards or frontwards, take off the
Height Gear Stopper and take out the Height Gear and
then turn the two Height Adjustment Screws. After the
adjustment is done, place the Height Gear back and fix it
with the Height Gear Stopper. After the tilt is adjusted in
such a way as above, adjust the height by loosening or
tightening the Height Gear. Azimuth alignment is adjusted
by loosening or tightening the PH Azimuth Screw. This
system has been carefully designed so as to minimize in
-fluence each other between azimuth and height adjust
-ment.
(3) Record Head Height Adjustment and Azimuth
Alignment
Record head tilt adjustment can be performed in the
same way as for the Playback Head.
Height adjustment can be adjusted while recording 400
Hz test tone by loosening or tightening RH Height Adjust
ment Screw to obtain the maximum level on the both
Level Meters. Azimuth alignment can be adjusted while
playing back 15 kHz signal by loosening or tightening RH
Azimuth Alignment Screw to obtain the maximum