Vco Adjustment; Rf Agc Adjustment - Sanyo DS19204 Service Manual

VCO ADJUSTMENT

Note: VCO must be adjusted after IC101 (Signal
Processor), IC802 (EEPROM) or T151 (VCO Coil) is
replaced.
1. Tune receiver to an active channel.
2. Set the picture controls to the Auto level.
3. Connect digital voltmeter + lead to pin 58 (TP 10) of IC101
and – lead to ground (TE 7).
4. Confirm a reading of 3.6 ± 0.2 VDC.
5. If voltage is out of specifications adjust T151 for
3.6 ± 0.2 VDC.

RF AGC ADJUSTMENT

1. Tune receiver to strongest VHF station in your area.
2. Set contrast and brightness controls for maximum.
3. Turn off the receiver and disconnect the AC power cord
(120V AC line).
4. While pressing the MENU key, reconnect the AC power
cord. The Service Menu display will now appear.
5. Select NO. 5D RAD (RF AGC Delay) with
6. Adjust the data with + or – key in the direction which
causes snow to appear; then in the opposite direction
until the snow just disappears.
7. To turn off the Service Menu display, press the MENU key.
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 terminals.
2. Switch the generator to the crosshatch pattern.
3. Reset the picture controls to the Auto levels.
4. Connect voltmeter (high impedance) + lead to terminal
TP51 and – lead to terminal TP50 on main board. Set
voltmeter for 1.5V ~ 3V 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. 3E SB (Sub Brightness) with
8. Adjust the data with + or – key for 820 mVDC.
9. Press the MENU key to turn off the Service Menu display.
10. Check brightness level on every active channel, 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 Auto 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 23 VDC.
The receiver should shutdown, losing raster and sound.
Then the receiver should turn off automatically. This
reaction indicates that the Hold-Down circuit is function-
ing properly. If the receiver does 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.
or key.
HIGH VOLTAGE CHECK
Note: +B (+135V) Voltage Check and Grayscale Adjustment
1. Connect high voltage voltmeter – lead to ground, and
connect + lead to anode of picture tube.
2. Tune receiver to an active channel and confirm TV is
operating properly.
3. Eliminate the beam current by adjusting the contrast and
brightness controls to minimum.
4. Confirm high voltage is within 24.5 KV and 27.8 KV. If
reading is not within range, check horizontal circuit.
No high voltage adjustment is provided on this chassis.
or key.
— 7 —
must be completed before attempting High Voltage
Check.