Electrical Adjustment Instructions - Philips DVP620VR/78 Service Manual

ELECTRICAL ADJUSTMENT INSTRUCTIONS

General Note: "CBA" is an 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 com-
pleted. Also, do not attempt these adjustments
unless the proper equipment is available.
2.To perform these alignment / confirmation proce-
dures, make sure that the tracking control is set in
the center position: Press either "CHANNEL L5 ? ? " or
"CHANNEL K" button on the front panel first, then
the "PLAY" button on the front panel.
Test Equipment Required
1.Oscilloscope: Dual-trace with 10:1 probe,
V-Range: 0.001~50V/Div.,
F-Range: DC~AC-20MHz
2.Alignment Tape (VFMS0001H6)
Head Switching Position Adjust-
ment
Purpose:
To determine the Head Switching position during
playback.
Symptom of Misadjustment:
May cause Head Switching noise or vertical jitter
in the picture.
Test point Adj.Point
TP751(V-OUT) VR501
TP302(RF-SW) (Switching Point)
GND (MAIN CBA)
Measurement
Tape
Equipment
VFMS0001H6 Oscilloscope
Connections of Measurement Equipment
TP751
Main CBA GND
TP302
Mode Input
PLAY
-----
(SP)
Spec.
6.5H±1H
(412.7µs±63.5µs)
Oscilloscope
CH1 CH2
Trig. (+)
1-9-1
Figure 1
EXT. Syncronize Trigger Point
CH1
1.0H
6.5H±1H (412.7µs±63.5µs)
CH2
Switching Pulse
Reference Notes:
Playback the Alignment tape and adjust VR501 so that
the V-sync front edge of the CH1 video output wave-
form is at the 6.5H±1H (412.7µs±63.5µs) delayed
position from the rising edge of the CH2 head switch-
ing pulse waveform.
0.5H
V-Sync
H9622EA