Samsung SV-DVD50 Service Manual page 122

Circuit Operating Descriptions
(7) V-Lock Phase
V-lock pulse is used for adjusting the picture's vertical vibration in trick play (still,slow).
The value is varied by tracking up/down key in trick play mode the variable range from 3H to 12H .
In trick play mode, the V-LOCK pulse position of CH-1 is variable but CH-2 is fixed.
During search mode ,both CH-1, 2 and V-LOCK position are fixed to 6.5H.
CH2
1
H
2
7-20
HEAD SW EDGE
CH1
PEDESTAL LEVEL
Fig. 7-20 V-LOCK PULSE
V-LOCK PULSE