Electrical Adjustment Instructions - Philips VR109/55 Service Manual

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ELECTRICAL ADJUSTMENT INSTRUCTIONS

General Note: "CBA" is an abbreviation for "Circuit
Board Assembly".
Notes:
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 proce-
dures, make sure that the tracking control is set in
the center position: Press either channel " " or " "
button first, then the " PLAY " button (VCR's Front
Panel only).
Test Equipment Required
1. Oscilloscope: Dual-trace with 10:1 probe, V-Range:
0.001~50V/Div., F-Frange: AC~DC-20MHz
2. Alignment Tape ( 4822 395 10283 )
06/28/2012
1. Head Switching Position
Adjustment
Purpose: To determine the Head Switching point dur-
ing playback.
Symptom of Misadjustment: May cause Head
Switching noise or vertical jitter in the picture.
Test Point
TP751(V-OUT)
TP302(RF-SW)
GND
Tape
4822 395 10283
Connections of Measurement Equipment
TP751
Main CBA
GND
TP302
EXT. Synchronize Trigger Point
CH1
1.0H
CH2
Reference Note:
TP302, TP751, VR501 : Main CBA
• Play back the test tape and adjust VR501 so that the
V-sync front edge of the CH1 video output wave-
form is at the 6.5H(412.7µs) delayed position from
the rising edge of the CH2 head switching pulse
waveform.
1-9-1
World of Free Manuals
Adj. Point Mode
PLAY
VR501 (SW-P)
(SP)
Measurement
Spec.
Equipment
6.5H±1H
Oscilloscope
(412.7±60µs)
Oscilloscope
CH1
Figure 1
V-Sync
0.5H
6.5H
Switching Pulse
H67T0EA
Input
----
CH2
Trig. (+)