JVC TV-13142 Service Manual page 20

TV-13142
TV-13142W
2-2: CONFIRMATION AND ADJUSTMENT OF AUDIO/
CONTROL HEAD
When the Tape Running Mechanism does not work well,
adjust the following items.
1. Playback the VHS Alignment Tape (MHP).
2. Confirm that the reflected picture of stamp mark is
appeared on the tape prior to P4 Post as shown in Fig.
2-2-A.
a) When the reflected picture is distorted, turn the screw
1 clockwise until the distortion is disappeared.
b) When the reflected picture is not distorted, turn the
screw 1 counterclockwise until little distortion is
appeared, then adjust the a).
Turn the screw 2 to set the audio level to maximum.
3.
4. Confirm that the bottom of the Audio/ Control Head and
the bottom of the tape is shown in Fig. 2-2-C.
When the height is not correct, turn the screw 3 to
c)
adjust the height. Then, adjust the 1~3 again.
Audio/Control Head
Stamp Mark
Audio/Control Head
3
2
Audio/Control Head
Tape
20
MECHANICAL ADJUSTMENTS
Reflected picture of
Stamp Mark
P4 Post
Fig. 2-2-A
1
4
Fig. 2-2-B
0.25±0.05mm
Fig. 2-2-C
2-3: TAPE RUNNING ADJUSTMENT
(X VALUE ADJUSTMENT)
1. Confirm and adjust the height of the Reel Disk.
(Refer to item 1-1)
2. Confirm and adjust the position of the Tension Post.
(Refer to item 1-2)
3. Adjust the Guide Roller. (Refer to item 2-1)
4. Confirm and adjust the Audio/Control Head.
(Refer to item 2-2)
5. Connect CH-1 of the oscilloscope to TP4001, CH-2 to
TP1002 and CH-3 to HOT side of Audio Out Jack.
6. Playback the VHS Alignment Tape (MHP).
7. Press and hold the Tracking-Auto button on the remote
control more than 2 seconds to set tracking to center.
Set the X Value adjustment driver (X-JG153) to the 4 of
8.
Fig. 2-2-B. Adjust X value so that the envelope waveform
output becomes maximum. Check if the relation between
Audio and Envelope waveform becomes (1) or (2) of Fig.
2-3.
Envelope
(1)
CH-3
Audio
(2)
2-4: CONFIRM HI-FI AUDIO (Hi-Fi model only)
1. Connect CH-1 of the oscilloscope to TP1002 and CH-2 to
the Hi-Fi Audio Out Jack.
2. Playback the VHS Alignment Tape (MHP).
3. Press and hold the Tracking-Auto button on the remote
control more than 2 seconds to set tracking to center.
4. Press the Tracking Up button and count number of steps
which the audio output is changed from Hi-Fi (10KHz) to
MONO (6KHz).
5. Press and hold the Tracking-Auto button on the remote
control more than 2 seconds to set tracking to center.
6. Press the Tracking Down button and count number of
steps which the audio output is changed from Hi-Fi
(10KHz) to MONO (6KHz).
7. If the difference are more than 3 steps, set the X Value
adjustment driver (X-JG153) to 4 of Fig. 2-2-B. Change
the X Value and adjust it so that the value becomes within
2 steps.
Fig. 2-3