Sanyo DS20930 Service Manual page 8

GRAYSCALE ADJUSTMENT
1. Set the picture controls to the Sports levels or Reset
(use MENU key and
2. Turn off the receiver and disconnect the AC power cord
(120V AC line).
3. While pressing the MENU key, reconnect the AC power
cord. The Service Menu display will now appear.
4. Select No. 15 RB (Red Bias), No. 16 GB (Green Bias), and
No. 17 BB (Blue Bias) with
0 with + or – key.
5. Select No. 18 RD (Red Drive) and No. 20 BD (Blue Drive) with
or key and set each data to 64 with + or – key.
6. Set No. 19 GD (Green Drive Reduction) data to 8, No. 53 SB
(Sub Brightness) data to 32, NO. 54 SCO (Sub Color ) data to
7, NO. 55 STI (Sub Tint) to 20, and NO. 56 SSH (Sub
Sharpness) data to 12 with
7. Turn Screen Control (T402) to minimum (fully counterclock-
wise).
8. Select the Service Menu No. 73 (Bias Adjustments) with
or key.
9. Advance Screen Control (T402) clockwise to obtain just
visible one color line. If line does not appear, place this
control to maximum (fully clockwise).
10. Raise each Bias Level with 3, 6, and 9 keys to obtain just
visible white line. (See Figure 5 below.)
2
1 3
(N/A) RB(+)
RB(-)
4 5
6
GB(-) (N/A) GB(+)
7 8
9
(N/A)
BB(-) BB(+)
Figure 5. Remote Control Number keys' functions
in Service Menu No. 73
11. Select the Service Menu No. 72 DRV (Drive Adjustments)
with or key.
12. Adjust Red and Blue Drive Levels alternately with 1, 3, 7, or
9 key to produce normal black and white picture in highlight
areas. (See Figure 6.)
2 3
1
(N/A) RD(+)
RD(-)
4
5 6
(N/A)
(N/A) (N/A)
8
7
9
(N/A) BD(+)
BD(-)
Figure 6. Remote Control Number keys' functions
in Service Menu No. 72 DRV
13. Check for proper grayscale at all brightness levels.
To turn off the Service Menu display, press the MENU key.
Note: If Grayscale Adjustment is made after picture tube
replacement, make Brightness Level Adjustment.
FOCUS ADJUSTMENT
Adjust focus control (T402) for well defined scanning lines.
SERVICE ADJUSTMENTS (Continued)
or key or RESET key).
or key and set each data to
or , and + or – keys.
FOR RED BIAS ADJUSTMENTS
FOR GREEN BIAS ADJUSTMENTS
FOR BLUE BIAS ADJUSTMENTS
FOR RED DRIVE ADJUSTMENTS
FOR BLUE DRIVE ADJUSTMENTS
BRIGHTNESS LEVEL ADJUSTMENT
Note:Grayscale, RF AGC, Video Level, and High Voltage
Check must be adjusted before attempting Brightness
Level Adjustment.
1. Connect a color-bar generator to the antenna terminal.
2. Switch the generator to the crosshatch pattern.
3. Reset the picture controls to the Sports levels.
4. Connect voltmeter (high impedance) + lead to terminal
TP51 and – lead to terminal TP50 on main board. Set volt-
meter for 1.5V~3.0V range.
5. Turn off the receiver and disconnect the AC power cord
(120V AC line).
6. While pressing the MENU key, reconnect the AC power
cord. The Service Menu display will now appear.
7. Select No. 53 SB (Sub Brightness) with
8. Adjust the data with + or – key for 650mVDC.
9. Press the MENU key to turn off the Service Menu display.
10. Check brightness level on every active channels, readjust
(repeat steps 5~9), if necessary.
Note: Do not set to excessive brightness level, otherwise the
contrast level will be suppressed.
HIGH VOLTAGE HOLD-DOWN TEST
Every time the receiver is serviced, the HIGH VOLTAGE
HOLD -DOWN circuit must be tested for proper operation by
following these steps;
1. Connect receiver to 120V AC line. Tune receiver to active
channel. Reset the picture controls to the Sports levels.
2. Check that the voltage measured between TP7 and TE7
(ground side) is within 16.5 VDC to 21 VDC. If the voltage is
out of this range, the Hold-Down Circuit must be checked.
3. Connect a DC Voltage supply to TP7 and TE7 through a 100
ohm 1/4W resistor. Adjust the DC voltage to 23VDC. The
receiver should shutdown, losing raster and sound. Then the
receiver should turn off automatically. This reaction indicates
that the Hold-Down circuit is functioning properly. If the
receiver goes not shutdown, a malfunction is indicated and
its cause must be found and corrected.
4. To obtain picture again, remove the DC Supply and wait a
few minutes. Now turn on the receiver.
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or key.