Input Level Adjustment - Sanyo DS20424 Service Manual

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 volt-
age 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 func-
tioning 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.
MULTI-SOUND SECTION ADJUSTMENTS
Note: Multi-Sound Section must be adjusted after
IC801 (CPU / Signal Processor), IC3401 (MTS
Decoder), or IC802 (EEPROM) is replaced.

INPUT LEVEL ADJUSTMENT

1. Connect a signal to the antenna terminals with audio of
1 KH 100% modulation.
Z
2. Turn off the receiver and disconnect the AC power cord
(AC 120V line).
3. Connect voltmeter (RMS) to TP317 and ground.
4. While pressing the Menu key, reconnect the AC power
cord. The Service Menu will now appear.
5. Select NO. 80 ATT (Attenuation) with the
6. Adjust the + or – key for a voltmeter reading of 400 ± 20
mVrms at TP317.
SERVICE ADJUSTMENTS (Continued)
or
SEPARATION ADJUSTMENT
7. Turn off the receiver and disconnect the AC power cord
(AC 120V line).
8. Connect oscilloscope CH1 to TP317 and CH2 to TP318
and ground.
9. Connect an MTS TV/Stereo generator to antenna terminal.
10. While pressing the Menu key, reconnect the AC power
cord. The Service Menu will now appear.
11. Select pilot, 300Hz audio frequency and Left modulating
signal.
12. Select NO. 81 WDB (Wide Band) with the
13. Adjust the + or – key for minimum low frequencies at
TP317. See Figure 7.
14. Select 4 KHz audio frequency and Right modulating signal.
15. Select NO. 82 SPC (Spectral) with the
16. Adjust the + or – key for minimum high frequencies at
TP318. See Figure 7.
Repeat adjustments (steps 11–16) until no further decreases
in amplitude can be obtained. Press the MENU key to turn
off the Service Menu display.
TP317 (R)
TP318 (L)
Figure 7. Separation Adjustments
key.
— 10 —
or
Minimize L leakage
300Hz
Minimize R leakage
4KHz
or key.
key.