Crt Cutoff; White Balance (Ntsc) - Mitsubishi Electric WS-48511 Service Manual

MODELS: WS-48511 / WS-55511 / WS-55711 / WS-65511 / WS-65611 / WS-65711 / WS-65712 / WS-73711 / WS-B55
[CRT Circuit]

7. CRT Cutoff

Measuring
Oscilloscope
Instrument
Test Point
TP6R, TP6G, TP6B
------
Ext. Trigger
Measuring
50V/Div. 2msec/Div.
Range
Input Signal
None
Input Terminal
Video Input
Cutoff Preset VC Data
Item Abbr
1 SCT
2 SBRT
5 SCON
6 RDRH
7 GDR
8 BDRH
9 CRTH
10 CTGH
11 CTBH
[CRT Circuit]

8. White Balance (NTSC)

Measuring
DC ma meter
Instrument
------
Test Point
------
Ext. Trigger
Measuring
------
Range
Input Signal
NTSC White Raster
RF or Video
Input Terminal
CIRCUIT ADJUST MODE
Activate ........ MENU-2-1-5-7
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, VC Function.
3. Press "1", automatically blanks the screen and sets COL to 0.
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 180V, as shown below, or
186V ±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.
Data
42
26
2
30
35
40
25
55
20
To set the CRTs white level in the NTSC mode.
Purpose
Symptom:
Monochrome has a color tint.
Note: Use the "FORMAT" button to activate the Expand mode (full screen).
1. Supply a full White Raster Signal
2. Activate the Service Mode, VC function.
3. Set the data for Item "23 COL" to 0.
4. Adjust Items "6 RDRH" and "8 BDRH" for optimum white at the center of
the screen.
5. Reduce the input luminance level to 25%.
6. Adjust Items "9 CTRH" and "11 CTBH" for optimum white.
7. Insert a Milliammeter in series with each CRT Cathode. The maximum
allowable current for each CRT is given in the table below.
8. Set the white raster to 100% and adjust Items "12 RDRL" and "13 BDRL" for
optimum white at the center of the screen.
9. Reduce the luminance level to 25%.
10. Adjust Item "14 CTRL" and "16 CTBL" for optimum white.
11. Set the data for Item "23 COL" back to 31.
Activate ........ MENU-2-1-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
Maximum CRT Current
55"& 65"
CRT
CURRENT
RED 580 uA
GREEN 580 uA
BLUE 580 uA
Page 41
CIRCUIT ADJUST MODE
73"
CURRENT
900 uA
900 uA
900 uA