Advertisement
6. Servo Circuit Adjustments
'
ae
:
6-1. Switching point adjustment
_(Fig. 6)
6-2. X-value adjustment
(Fig. 6)
Purpose:
To set the switching point of the video heads during
playback to the center where the CH-1 and CH-2
envelopes overlap each other.
Fault due to incomplete adjustment:
Vertical sync signal is degraded and vertical jitter.
occurs.
7
.
:
Ree
Switching noise appears across the bottom of the
screen.
Test EquipmentJigs and Connection Points
Purpose:
"
To ensure compatibility with other VCRs.
Fault due to incompiete adjustment:
When a tape recorded by another VCR is played back,
the tracking is not optimized and noise appears on the
screen.
2
Test Equipment/Jigs and Connection Points
Oscilloscope
CH-1: PG2508-1 (PB FM)
CH-2: PG2508-8 (SW25Hz)
Alignment tape (MH-2)
Oscilloscope
CH-1: Video out jack
State of VCR
CH-2: PG2508-8(SW25Hz)
1) Play the alignment tape.
'
Alignment tape (MH-2)
2) Set to the X-value adjustment test mode. -
State of VCR
Adjustment Point
1) Play the alignment tape
2) Set to the X-value adjustment test mode.
Adjustment Point
F.FWD button,
REW button.
Adjustment Procedure
1) Play the alignment tape.
2) Press the "CH &"and "CH'W"
buttons of the remote
control provided simultaneously and hold them, then
press the "CHANNEL
V "(S2709) button of the VCR
to set the VCR to the test mode. (SP is switched to
LP in the display.)
8) Press the "F.FWD"and "REW" buttons of the remote
control so the phase from the vertical sync to the
trailing edge (trigger position) of the SW25Hz pulse
is set to 6.5H.+ 0.5H.
4) Press the "STOP" button to release the test mode.
Groove for the adjustment X-value
Adjustment Procedure
1) Play the alignment tape.
2) Press the "CH & "and "CH ¥ " buttons of the remote
control provided simultaneously and hold them, then
press the "CHANNEL V "(S2709) button of the VCR
to set the VCR to the test mode. (SP is switched to
LP in the display.)
:
i
3) Loasen the screw holding the A/C head base (do not
loosen it excessively).
i
4) Insert a screwdriver into the groove for adjusting the
X-value and adjust so the FM output is maximum.
There are two maximum FM output points when the
groove for adjusting the X-value is turned:
Adjust.
the FM output to a maximum when the groove is at
the correct position as shown in the figure below.
5) Press the "STOP" button to release the test mode.
Waveforms
(8Vidiv.,S0us/div.)
SW30Hz =|
VIDEO OUT
{600mVidiv.)
VERTICAL SYNC.
6.5H + 05H
3
«Conditions of oscilloscope>
Trigger with CH-2.
Set the sync slope to "-".
TRIGGER
POINT
Waveforms
~
Ft output
mex imam
4
H
(S0nV/6iv. .20us/div.)
GROGVE FOR ADUSTHENT
THE XAVALUE
A/C HEAD BASE
RETAINING SCREW
MAXIMUM FAI_OUTPUT POINTS
&)
eu
er
fcommect ]{ — [incornect
Advertisement
Chapters
