Black Level; Sub Contrast - Mitsubishi Electric WT-42311 Service Manual

[Video Circuit]

7. Black Level

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

8. Sub Contrast

Measuring
DC ma meter
Instrument
Test Point DT connector pins 7 & 8
------
Ext. Trigger
Measuring
-----
Range
Input Signal
Grayscale
RF Input
Input Terminal
MODEL: WT-42311 / WT-A42
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. (SBRT data should fall between 24 and 28.)
4. Press ENTER to save data.
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 500µA ±10µA .
6. Remove the meter.
7. Save data and Exit the Service Mode.
CIRCUIT ADJUST MODE
Activate ........ MENU-2-2-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
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