Panasonic OmniVision PV-M1347, Service Manual

Page: 42 / 143

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2. A/C HEAD TILT CONFIRMATION
Purpose:
To confirm that the tape runs smoothly. In particular, confirm
that the tape properly picks up the Audio Signal at the upper
part of the head and the Control Signal at the lower part of
the head.
Symptom of Misadjustment:
If the tilt of the A/C Head is poorly adjusted, the tape will
eventually be damaged. An intermittent Blue screen may be
seen in Playback.
1. Play back a T120 cassette tape and check that the tape
travels smoothly between the upper and lower guides of the
P4 post.
2. If necessary, adjust Black Screw (B) clockwise until the
tape begins to curl at the lower edge of the P4 post. Then
adjust the screw counterclockwise until the curling is
eliminated.
Fig. M8
3. A/C HEAD HEIGHT CONFIRMATION
The height of the A/C Head replacement part is preset at the
factory.
Purpose:
To be sure the tape runs properly along the Control Head.
Symptom of Misadjustment:
If the control signal is not properly picked up, Servo Operation
cannot be achieved. A Blue screen will be seen in Playback.
This confirmation is required when the A/C Head is replaced.
1. Play back a T120 cassette tape and check that the lower
edge of the tape runs approximately 0.25 mm above the
lower edge of the A/C Head.
2. If necessary, adjust Black Screws (A) and (B) clockwise to
lower the tape or counterclockwise to raise.
4. A/C HEAD AZIMUTH ADJUSTMENT
Purpose:
To adjust the position and height of the A/C Head so that it
meets the tape tracks properly.
Symptom of Misadjustment:
If the position of the A/C Head is not properly adjusted, the
Audio S/N Ratio is poor.
1. Connect the oscilloscope to TP4002 on the Audio Amp
Section of the Main C.B.A.
2. Play back the 6kHz Monaural Audio portion of the alignment
tape.
3. Adjust Black Screw (C) on the A/C Head base so that the
output level is at maximum.
Fig. M10
4. Confirm the height of the A/C Head is proper. If not, readjust
Black Screws (A) and (B).
Black Screw (B)
Black Screw (C)
Black Screw (A)
Control Head
Lower Edge
of Control Head
0.25mm
Lower Edge
of Tape
Tape Running
Condition A/C Head in
Tilted Condition
Direction to
turn for
Correction
Fig. M9
Maximum
6KHz-Audio