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4-3. TAPE PATH ADJUSTMENT
In normal circumstances, the tape path system does not
need to be adjusted. However, after removing or replacing
one of the parts shown in Fig.4-3-1, you should check and
adjust the tape path. The adjustment of the tape path is
carried out while monitoring the envelope waveform of
the video head output, using an oscilloscope. To make sure
that the tape drawn off the reel runs freely and without
excessive tension along all the tape guides and cylinders
(drums), it is also important to check each tape guide by
eye.
T guide roller —
Audio
R/P head assembly
S guide roller
(ACE head)
Full erase
head
S tape
guide
BT post
Capstan shaft
|
Cylinder
(Drum)
0 tape guide | ,
Fig.4-3-1
4-3-1. ADJUSTMENT PROCEDURE
1.
Select a PAL or NTSC alignment tape or blank cassette
tape, according to the transmission system of the VCR
you are repairing.
NTSC:
For models
with 525 scanning
lines and a field
frequency of 60Hz
PAL:
For models with 625 scanning Ines and a field
frequency of 50Hz
2.
Clean the tape guides, the cylinder (drum), the capstan
Shaft, the audio R/P head (ACE head) and the full
erase head.
3.
Using an oscilloscope, adjust the height of the guide
roller and
carry
out
horizontal
position
adjust-
ment,height adjustment and azimuth adjustment on
the audio R/P head (ACE head). When observing the
envelope waveform, bring the CH-1 probe into contact
with the envelope waveform test point, and bring the
CH-2
probe
into contact with the switching
pulse
(SW P) test point. While adjusting the tape path, set
the trigger
at the low side
of the switching
pulse
(SW P) in order to observe the output waveform on
the CH-1 side of the video head.
NOTE:The
contact point for the oscilloscope varies from
one model to another, so to find the correct point for your
model, refer to the figure entitled "Test point for tape path
adjustment" in the electrical circuit section of the service
manual.
4.
When
checking
the tape path by eye, use
a dental
mirror.
4-3-2. LOAD LEVER ASSEMBLY HEIGHT
ADJUSTMENT
(See Fig.4-3-2)
1.
Refer to sections 3-9-2, and remove the opener mount-
ing.
2. Position the height adjustment tool (VHJ-0102)@
under the full surface of the protrusion @ on the load
lever assembly @, as shown in Fig.4-3-2.
3.
Using your fingers, gently screw
the adjustment
nut @) clockwise into the nut box (VHJ-0048) © until
the protrusion® of the load lever assembly®
touches the height adjustment tool (VHJ-0102)@)
and the
screw starts to feel tight.
Next, loosen the
adjustment nut @ by 270° anticlockwise.
4.
Load a cassette tape (NTSC: T-160, PAL: E-240) and
switch to PLAY mode. Check that when you do this, no
scratches appear on the upper or lower edges of the
tape. If scratches do appear, re-adjust the height.
Arrange the equipment so that the whole surface of the
projection on the load lever assembly is positioned over
the height adjustment tool (VHJ-0102) when seen from
directly overhead.
© Nut box
(VHJ-0048)
@Load lever
@Height adjustment
+--+
tool (VHJ-0102)
@Adjustment nut
Fig.4-3-2
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