Philips DVP3355V/F7, Service Manual, Page: 18 / 78

1-7-1 E8E6EEA
ELECTRICAL ADJUSTMENT INSTRUCTIONS
General Note: “CBA” is abbreviation for
“Circuit Board Assembly.”
NOTE:
1. Electrical adjustments are required after replacing
circuit components and certain mechanical parts.
It is important to do these adjustments only after
all repairs and replacements have been
completed. Also, do not attempt these adjustments
unless the proper equipment is available.
2. To perform these alignment / confirmation
procedures, make sure that the tracking control is
set in the center position: Press either [TRACKING
L
] or [TRACKING
K
] button on the front panel
first, then the [PLAY
B
] (VCR) button on the front
panel.
Test Equipment Required
1. Oscilloscope: Dual-trace with 10:1 probe,
V-Range: 0.001~50 V/Div.,
F-Range: DC~AC-20 MHz
2. Alignment Tape (FL8A)
Head Switching Position
Adjustment
Purpose: To determine the Head Switching position
during playback.
Symptom of Misadjustment: May cause Head
Switching noise or vertical jitter in the picture.
Note: TP751(V-OUT), TP302(RF-SW),
VR501(Switching Point) --- Main CBA
Reference Notes:
Playback the Alignment tape and adjust VR501 so that
the V-sync front edge of the CH1 video output
waveform is at the 6.5H ± 1H (412.7
µ
s ± 63.5
µ
s)
delayed position from the rising edge of the CH2 head
switching pulse waveform.
Test point Adj. Point Mode Input
TP751(V-OUT)
TP302(RF-SW)
GND
VR501
(Switching Point)
PLAY
(SP)
-----
Tape
Measurement
Equipment
Spec.
FL8A Oscilloscope
6.5H ± 1H
(412.7
µ
s±63.5
µ
s)
Connections of Measurement Equipment
Figure 1
Oscilloscope
Main CBA
TP751
CH1 CH2
Trig. (+)
GND
TP302
EXT. Syncronize Trigger Point
1.0H
CH1
CH2
Switching Pulse
V-Sync
0.5H
6.5H
±
1H (412.7
µ
s
±
63.5
µ
s)