Black Level; Sub Contrast - Mitsubishi Electric WT-46807 Service Manual

MODELS: WT-46807 / WS-55807 / WS-55857 / WS-55907 /WS-65807 / WS-65857 / WS-65907 / WS-73907
[Video Circuit]

11. Black Level

Measuring
-----
Instrument
Test Point
-----
------
Ext. Trigger
Measuring
------
Range
Input Signal
Monoscope
Input Terminal
Video Input
CIRCUIT ADJUST MODE
Activate ........ MENU-8-2-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
[Video Circuit]

12. Sub Contrast

Measuring
DC ma meter
Instrument
DT connector pins 7 & 8
Test Point
------
Ext. Trigger
Measuring
-----
Range
Input Signal
Grayscale
RF Input
Input Terminal
CIRCUIT ADJUST MODE
Activate ........ MENU-8-2-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
Purpose:
To set the black level of the picture.
Excess or insufficient brightness.
Symptom:
1. Supply a Monoscope signal to a Video Input.
2. Activate the Adjust Mode, Video/Chroma Function.
3. Adjust Item "2 SBRT" so the 0% and 10% black levels on the gradation scale
are the same. Make note of the data value.
4. Press ENTER to save data.
5. Use the "3" button to toggle to the HD and 480P modes.
6. Set the data for "2 SBRT" in both modes to the NTSC data value (Step 3).
NOTE: Press ENTER to save data before switching modes.
7. Exit the Service Mode.
40% 30% 20% 10%
50% 0% 0% 0%
60% 70% 80% 90%
GRADATION SCALE
To set overall beam current to its' optimum level.
Purpose
Symptom:
Excess or insufficient contrast.
Note: Activate the Expand mode (full screen).
1. Supply a Grayscale signal to a RF Input.
2. Activate the Adjust Mode, Video/Chroma Function.
3. Select Item "1 SCT", signal level automatically reduces.
4. Connect a 3ma DC meter between DT connector pins 7 and 8. Positive lead to
pin 7.
5. Adjust Item "1 SCT" for 645µA ±20µA (900µa ±20µa on the WS-73907).
Note the data value.
6. Press Enter to save data.
7. Remove the meter.
8. Use the "3" button to toggle to the HD and 480P modes.
9. Set the data for "1 SCT" in both modes to the NTSC data value (Step 5).
NOTE: Press ENTER to save data before switching modes.
10. Save data and Exit the Service Mode.
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