Sharp VT-G14, Руководство по обслуживанию

Страница: 46 / 121

46
VT-G14
VT-G21
ADJUSTMENT OF THE VCR ELECTRICAL CIRCUITRY
SERVO CIRCUIT ADJUSTMENT
ADJUSTMENT OF HEAD SWITCH-
ING POINT
Figure 2-1.
Measuring Dual trace oscilloscope
instrument
Mode Playback
Cassette Alignment tape(VROUBZFS)
Test point TP2201 (Video Out) to CH1
TP3302 (Trigger) to CH2
Control Remote Control
Specification 5.5 ± 0.5H (lines)
1. Put the set in the SERVICE mode by turning the
power on with the STAND BY/POWER button while
the CH
'
button on the front pannel is being pressed
down more than 3 seconds.
2. Play the alignment tape (VROUBZFS), then press
the PROG button on the remote control to turn the
set into the adjustment mode for the head switching
point.
"TEST" is displayed on the screen, in the playback
mode it means the set is in the adjusting mode for
the head switching point.
3. Connect a dual trace oscilloscope to the test points
TP2201 (Video out) and TP3302. (Trigger the
oscilloscope with the head switching pulse on
TP3302.)
4. Press the PLAY button of remote control to make the
adjustment of the head switching point, then the
leading edge of the head switching pulse is
automatically set 5.5H (line) ahead of the vertical sync
as shown in Figure 2-1 and the adjustment data is
memorized in the E
2 P-ROM IC.
5. Then press the STOP button to stop the tape, and
turn the power off to cancel the SERVICE mode.
Notes:
»
Before the adjustment:
Electrical adjustments described here are often required after replacement of electronic components and mechanical
parts such as video heads.
Check that the mechanism and all electric components are in good working condition prior to the adjustments,
otherwise adjustments can not be completed.
»
Instruments required:
Dual trace oscilloscope
Blank video cassette tape
Colour bar generator
Alignment tape (VROUBZFS)
»
Adjustment of the VCR should be done in the TV/VCR combinated style. But there is a function the able to
cut off high voltage of TV. Namely, you can check only VCR part by taking the plug of P1003 off the socket
SC1003 in Main PWB (PWB-A). Therefore you can use this function on the occasion of checking and
adjustment of VCR part.
Notes:
1
Data of this adjustment is memorized to the E 2 P-ROM
IC on the main PWB when the head switching point
is automatically adjusted.
2
In order to set the unit in the adjusting mode for the
head switching point, pressing the PROG button is
needed at the playback in the SERVICE mode.
5.5
±
0.5H(Iines) V-sync.
CH-2
HEAD
SWITCHING
PULSE
CH-1
VIDEO OUT CH-1: 1V/div 50
µ
sec/div
CH-2: 2V/div 50
µ
sec/div