Rolsen 21C19/PF21C19, Руководство по обслуживанию

Страница: 9 / 46

SERVICE MANUAL
7
CIRCUIT ADJUSTMENTS
Preparation:
Circuit adjustments should be made only after completion of set-up adjustments.
Circuit adjustments can be performed using the adjustable components inside the TV set. For TVs with
I
2
C bus control, first change the bus data.
1. Degaussing
A degaussing coil is built inside he TV set. Each time the TV is powered on, the degaussing coil will
automatically degauss the TV. If the TV is magnetized by external strong magnetic field, causing
color spot on the screen, use a specific degausser to demagnetize the TV in the following ways.
Otherwise, color distortion will be shown on the screen.
1.1 Power on the TV set and operate it for at least 15 minutes.
1.2 Receive red full-field pattern.
1.3 Power on the specific degausser and face it to the TV screen.
1.4 Turn on the degausser. Slowly move it around the screen and slowly take it away from the TV.
1.5 Repeat the above steps until the TV is degaussed completely.
2. Supply Voltage Adjustment
Caution: +B voltage has close relation to high voltage. To prevent X-ray radiation, set +B voltage to
the rated voltage.
2.1 Make sure that the supply voltage is within the range of the rated value.
2.2 Connect a digital voltmeter to the +B voltage output terminal of the TV set. Power on the TV and set
the brightness and sub-brightness to minimum.
2.3 Regulate voltage adjustment components on the power PCB to make the voltmeter read 115±1V.
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
picture tube.
3.2 Plug in the supply socket (150-250V, AC, 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 EHT limitation.
3.4 Change the brightness from minimum to maximum, and ensure high voltage not beyond the
limitation in any case.
Nominal EHT voltage: 2
7.5
±
1
KV Limited EHT voltage:
30
KV
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.