Changhong Electric PF2939, Руководство по обслуживанию, Страница: 39 / 47

SERVICE MANUAL
A degaussing coil is mounted around the CRT so that external degaussing after moving the TV
is generally unnecessary, providing it is properly degaussed upon installation. The degaussing
coil operates in about 1 second after power on. If the set is moved or faced to a different
direction, the power switch must be switched off for at least 30 minutes in order that the
automatic degaussing circuit operates properly. Should the chassis or parts of the cabinet
become magnetized to cause poor color purity, use an external-degaussing coil. Slowly move
the degaussing coil around the screen, the sides and front of the TV and slowly withdraw the
coil to a distance of about 2m before unplug it. If color shading still exists, perform the Color
Purity Adjustment and Convergence Adjustment procedures.
3. Supply Voltage Adjustment
Caution: +B voltage has close relation to high voltage. To avoid X-ray radiation, +B voltage
should be +145V.
1) AC power supply to
110-24
0V
50/60Hz
.
2) Connect a digital voltmeter to two pins of C820, and then turn on the TV.
3) Receive Philips test pattern.
4) The voltmeter should be read 145±1.5V .
4. High Voltage Inspection
Caution: No high voltage adjustment should be done in the chassis.
1) Connect a precise high voltmeter to the second anode of the CRT.
2) Turn on the TV and set the brightness and contrast to minimum (i.e. set beam current of the
CRT to zero).
3) The high voltage tested should be 29
±
1 KV. .
5. Focus Adjustment
1) Use the remote control to set the contrast to maximum and the brightness ， color to medium.
2) Set H. V. lines near center of Philips pattern to thinnest with the FCB on the FBT. After finishing
adjustment
，
ensure that no poor focusing exists near the center or around of the frame.
Before Adjusting After Adjusting
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