SERVICE MANUAL
3. High Voltage Inspection
Caution: No high voltage adjustment components inside the chassis. Please perform
high voltage inspection in the following ways.
3.1 Connect a precise static high voltmeter to the second anode (inside the high voltage cap) of the
CRT.
3.2 Plug in the supply socket (150-250V ~, 50Hz) and turn on the TV. Set the brightness and
contrast to minimum (0
μ
A).
3.3 The high voltage reading should be less than the limited EHT voltage.
3.4 Change the brightness from minimum to maximum, and ensure high voltage not beyond the
limitation in any case.
Nominal EHT voltage Limited EHT voltage Remarks
25KV
±
1KV 30KV for 25" pure flat CRT only
29KV
±
1KV 32KV for 25" super pure flat CRT only
28.8KV
±
1KV 32KV for 29” CRT only
Note: The data sheet may differ dependent on different CRTs.
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.
Before Adjusting After Adjusting
Fig. 4
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, 50Hz (limit
current of 10mA) between all naked metal and cold ground. Test every point for 3 sec. 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 20M
Ω
.
9
Summary of Contents for 25F83
Page 18: ...SERVICE MANUAL 3 Black Diagram 7 21 ...
Page 19: ...SERVICE MANUAL 8 22 ...
Page 20: ...SERVICE MANUAL 4 Pining 5 Refer to Table 12 about Functions and Data of the IC s Pins 9 23 ...
Page 46: ...CIRCUIT DIAGRAM JUC 820 975 JUC 820 591 JUC 820 725 JUC 820 644 APPENDIX ...
Page 47: ...Circuit Diagram for CRT RGB PCB of 25F83 PF25F83 ...