Main/Sub Color Level; Crt Cutoff - Mitsubishi Electric WT-42313 Service Manual

[Video Circuit]

3. Main/Sub Color Level

Measuring
Oscilloscope
Instrument
JA pin 18
Test Point
JA pin 8
------
Ext. Trigger
Measuring
------
Range
Color Bars
Input Signal
Input Terminal
Video
[CRT Circuit]

4. CRT Cutoff

Measuring
Oscilloscope
Instrument
Test Point TP6R, TP6G, TP6B
Ext. Trigger ------
Measuring
50V/Div. 2msec/Div.
Range
None
Input Signal
Video Input
Input Terminal
MODEL: WT-42313 / WT-42413
Purpose:
To match the sub picture color to that of the main picture.
Symptom:
Main and sub pictures colors differ.
1. Supply an NTSC signal to an External Video Input.
2. Select the NTSC signal as the source for both the main and sub pictures.
3. Connect an oscilloscope to connector JA pin 18 (Main PR).
4. Activate the Adjustment mode.
5. Select Item "2 COLM" in the Main Matrix Function.
6. Adjust data so the PR signal is 0.71 Vp-p max. - 0.66 Vp-p min
(If it cannot be adjusted within this range, set to the lower value)
7. Connect an oscilloscope to connector JA pin 8 (Sub PR). If the waveform is
unstable, activate PIP.
8. Select item "2 COLS" in the Sub Matrix Function.
9. Adjust so Sub PR = Main PR.
CIRCUIT ADJUST MODE
Activate ........ MENU-0-3-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
Purpose
To set the cutoff point for all three CRTs.
Monochrome has a color tint, or incorrect brightness.
Symptom:
Note: Use the Expand mode (full screen)
1. Select an External Input with no signal.
2. Enter the Adjustment Mode, Video Chroma Function.
3. Press "1", automatically blanks the screen and sets COL to 0.
Note: If the screen goes blue, turn off Video Mute.
4. Set the data to the values given in the table below.
5. Connect the oscilloscope to TP6R.
6. Adjust the Red Screen VR so the black level is 170V, as shown below, or
176V ±1VDC using an DC Voltmeter.
7. Repeat Steps 4 and 5 to set the Blue and Green Screen VRs, using
TP6G and TP6B.
Note: White Balance must be performed after this adjustment.
Cutoff Preset VC Data
Item Abbr
1 SCT
2 SBRT
3 SCON
4 RDRH
5 GDRH
6 BDRH
7 CTRH
8 CTGH
9 CTBH
Page 26
Data
31
31
0
CIRCUIT ADJUST MODE
31
Activate ........ MENU-0-3-5-7
41
Function .................AUDIO
31
Item No. .................VIDEO
31
Adjust Data ...........ADJUST
46
Save Data .... .........ENTER
31
Exit ..............MENU (twice)