Focus Adjustment; Safety Inspection; Design/Service Mode; Bus Data In The S Mode - Changhong Electric 21NF55 Service Manual

4. Focus Adjustment

Caution: Dangerously high voltages are present inside the TV. Extreme caution should be
exercised when working on the TV with the back removed.
4.1 After removing the back cover, look for the FBT on the main PCB. There should be a FCB on the
FBT.
4.2 Power on the TV and preheat it for 15 min.
4.3 Receive a normal TV signal. Rotate knob of the FCB until you get a sharp picture.

5. Safety Inspection

5.1 Inspection for insulation and voltage-resistant
Perform safety test for all naked metal of the TV. Supply high voltage of 3000V AC, 50Hz (limit
current of 10mA) between all naked metal and cold ground. Test ev ery point for 3 min. and ensure
no arcing and sparking.
5.2 Requirements for insulation resistance
Measure resistance between naked metal of the TV and feed end of the power cord to be infinity
with a DC-500 high resistance meter and insulation resistance between the naked metal and
degaussing coil to be over 20MΩ.

6. DESIGN/SERVICE mode

6.1 To enter the USER SERVICE mode
Caution: The user service mode adjustment can be changed only when service personnel adjust
the whole set data during servicing. As the control data have dramatic effects on functions and
performance of the TV, service personnel should not tell user how to
enter the SERVICE mode to avoid improper data settings.
6.1.1 Set the volume to 0. Then press and hold the MUTE button on
the remote control, and press the MENU button on the TV to
enter the SERVICE mode. (In this case, the S mode cannot be
stored in the EEPROM. To exit from the S mode, turn off the TV set. )
After entering the S mode, Red "S" is displayed on the upper center of the screen and MENU1
6.1.2
is default. Use the POS+/- buttons to highlight an adjustment and the VOL+/- buttons to adjust
it. The adjusted data are immediately output and stored in the EEPROM

6.2 Bus data in the S mode

Item Adjustment
CORE 03
0-IF 20
5PAR/6PAR 1F
5BOW/6BOW 1F
Set to
5HSH/6HSH
optimal mode
SERVICE MANUAL
Table 1 Adjustment and Option Data in S mode
Description
Coring (for some CPU only)
Sound adjustment setting (for some CPU only)
Parallelogram correction (for large-screen only)
Curve correction (for large-screen only)
Horizontal center in the TV mode for 50Hz/60Hz
the
For 50Hz, "5HSH" is displayed；for 60Hz, "6HSH" is
displayed.
9
S
VS 0-3F 25
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Remarks
*
(Continued)