Sony SVT-RA168, Service Manual

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2-35
SVT-RA40/RA168
4-3-1. Adjustment Procedure
1. Alignment tape or blank cassette tape, according to the
transmission system of the VCR you are repairing.
Models with 525 scanning lines and a field frequency
of 60H
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 adjustment,
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 (ENV) 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.
n
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 “Step 5 Test point for
tape path adjustment” in this section.
4. When checking the tape path by eye, use a dental
mirror.
4-3-2. Load Lever Assembly Height
Adjustment
1. Refer to Sections 3-9-2, and remove the opener
mounting .
2. Position the height adjustment tool (VHJ-0111)
3
under the full surface of the protrusion
2
on the load
lever assembly
1
, as shown in Fig. 4-3-2.
3. Using your fingers, gently screw the adjustment nut
4
clockwise into the nut box (VHJ-0048)
5
until the
protrusion
2
of the load lever assembly
1
touches
the height adjustment tool (VHJ-0111)
3
and the
screw starts to feel tight. Next, loosen the adjustment
nut
4
by 270 d counterclockwise. .
4. Load a cassette tape (T-160). Wind the tape to the
beginning, and repeat FF
↔
REV five times (repeat
for the same portion 30 to 60 seconds).
If the bottom edge of the tape breaks, rotate the
adjustment
4
nut in the counterclockwise direction
by about 90 d . Repeat FF
↔
REV five times again and
check that the tape edge does not break (adjust again if
it does). Next, repeat CUE
↔
REV five times and
check that the tape is not damaged. If damaged, rotate
the adjustment nut in the clockwise direction by about
90 d . Repeat FF
↔
REW and CUE
↔
REV and check
that the tape is not damaged.
Fig. 4-3-2
2
Protrusion
Arrange the equipment so that the whole surface of the
projection on the load lever assembly is positioned over
the height adjustment tool (VHJ-0111) when seen from
directly overhead.
3
Height adjustment
tool (VHJ-0111)
1
Load lever
assembly
4
Adjustment nut