Philips DVP620VR Service Manual page 22

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 w" or
"CHANNEL a" 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 (9965 000 14514)
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.
TP751(V-OUT) VR501 a
TP504(RF-SW) | (Switching Point)| 58)
GND (MAIN CBA)
Measurement
| tere | Mestigeeer" | Spee
9965 000 14514] Oscilloscope | (4, 2 rnsi63 Sus)
Connections of Measurement Equipment
TP751 ry
Main CBA
TP504 ,
Oscilloscope
CH1 CH2
Trig. (+)
1-9-1
te EXT. Syncronize Trigger Point
—t 1.0Hk- | & 0.5H
6.5H+1H (412.7s+63.5ys)
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 (412.7ys+63.5us) delayed
position from the rising edge of the CH2 head switch-
ing pulse waveform.
H9720EA