Hitachi VT-FX665AC Service Manual page 45

1-A. Preliminary/Final Checking and
Alignment of Tape Path
Purpose:
To make sure that the tape path is well stabilized.
Symptom of Misalignment:
If the tape path is unstable, the tape will be damaged.
Note: Do not use an Alignment Tape for this procedure.
If the unit is not correctly aligned, the tape may be
damaged.
1. Play back a blank cassette tape and check to see
that the tape runs without creasing at Guide Roll-
ers [2] and [3], and at points A and B on the lead
surface. (Refer to Fig M3 and M4.)
2. If creasing is apparent, align the height of the guide
rollers by turning the top of Guide Rollers [2] and
[3] with a Guide Roller Adj. Screwdriver. (Refer to
Fig. M3 and M5.)
Note: Beneath each Guide Roller, there is a
small screw. (Refer to Fig. M5.) This screw works
Guide Roller [2]
A
Take-up Guide Post [4]
Lead Surface of Cylinder
Correct
Guide Roller
Tape
Small Screw
Take-up Guide
Post
Tape
Guide Roller [3]
AC Head
B
Fig. M3
Tape
Fig. M4
Incorrect
Fig. M5
to apply adequate torque to the shaft of each
Guide Roller so that the Guide Roller turns prop-
erly. Even when adjusting the height of the Guide
Roller(s), do not touch these two small screws.
3. Check to see that the tape runs without creasing at
Take-up Guide Post [4] or without snaking be-
tween Guide Roller [3] and AC Head.
(Fig. M3 and M5)
4. If creasing or snaking is apparent, adjust the Tilt
Adj. Screw of the AC Head. (Fig. M6)
Azimuth Adj. Screw
AC Head
Tilt Adj. Screw
1-B. X Value Alignment
Purpose:
To align the Horizontal Position of the Audio/Con-
trol/Erase Head.
Symptom of Misalignment:
If the Horizontal Position of the Audio/Control/Erase
Head is not properly aligned, maximum envelope can-
not be obtained at the Neutral position of the Tracking
Control Circuit.
1. Connect the oscilloscope to TP301 (C-PB) and
TP303 (CTL) on the Main CBA. Use TP302 (RF-
SW) as a trigger.
2. Play back the Gray Scale of the Alignment Tape
(30HMP2-1) and confirm that the PB FM signal is
present.
3. Set the Tracking Control Circuit to the center posi-
tion by pressing the CH UP button then the PLAY
button on the VCR. (Refer to note on bottom of
page 2-3-4.)
4. Use the X-Value Adj. Screwdriver so that the PB FM
signal at TP301 (C-PB) is maximum. (Fig. M6)
5. Press CH UP button on the VCR until the CTL wave-
form has shifted by approx. +2msec. Make sure
that the envelope is simply attenuated (shrinks in
height) during this process so that you will know
the envelope has been at its peak.
2-3-3
X-Value Adj.
Screwdriver
Fig. M6