Board HV Regulation Circuit Check and Adjustment

SECTION 4 SAFETY RELATED ADJUSTMENTS

[ G BOARD]

4-1. HV REGULATION CIRCUIT CHECK AND ADJUSTMENT

When replacing the following components marked with on the schematic diagram always check HV regulation, and if nec- essary re-adjust.

: C514

: C514, C515, C516

IC651

T502,T503, T504 (FBT)

D.Y

OPERATION CHECK

1.Connect a HV static voltmeter to the unconnected plug of the high-voltage block. (Fig.4-1)

2.Power on the set.

3.Receive the dot signal. (PICTURE and BRIGHTNESS to minimum)

4.Check that the HV static voltmeter is reading 31.00±1.0kVdc.

HV Regulation adjustment

1.Connect a HV static voltmeter to the unconnected plug of the hight-voltage block.

2.Power on the set.

3.Receive the dot signal. (PICTURE and BRIGHTNESS to minimum)

4.If anode voltage is 32kV or higher, replace C514 of 390PF/ 2kV with that of 680PF/2kV, and check if the voltage is within the standard range.

5.If anode voltage is 30kV or lower, replace C514 of 390PF/ 2kV with that of 100PF/2kV, and check if the voltage is within the standard range. (Fig.4-2)

Remove the cap off from the unused terminal and connect a static voltmeter there.

	Fig. 4-1
G BOARD	– COMPONENT SIDE –
	R561
C514	CN505	R514
		R514

TP135V

R512

51 IC651

Fig. 4-2

4-2. HV HOLD DOWN CIRCUIT OPERATION CHECK AND ADJUSTMENT

When replacing the following components marked with on the schematic diagram always check hold-down voltage and if necessary re-adjust.

: R514, R561

: C507, C513 D501, D504, D507 IC301, IC501, IC651

R502, R514, R516, R517, R539, R560, R561 T502, T503, T504 (FBT)

D.Y

OPERATION CHECK

1.Remove CN651 connecter.

2.Short-circuit across TP-PROT (R692) and ground.

3.Connect a HV static voltmeter to the unconnected plug of the high-voltage block.

4.Connect a 220k variable resistor, across pin 3 and pin 5 of IC651 set to maximum value.

5.Power on the set.

6.Receive the dot signal. (PICTURE and BRIGHTNESS to minimum)

7.Gradually lower the value of the variable resistor and check

that the hold-down circuit operates at a static voltmeter read- ing of 33.5±1.0kVdc when the raster disappears.

HV HOLD-DOWN ADJUSTMENT

1.Repart steps 1 ~ 7 as above.

2.If hold down voltage is 34.5kV or higher, remove R514, mount a resistor (390kΩ, 1/4W : RN) onto R561 instead,

and check again if the hold-down voltage is within the stan- dard range.

3.If hold down voltage is 32.5kV or lower, mount a resistor (220kΩ, 1/4W : RN) onto R561 and check again if the hold-

down voltage is within the standard range. (Fig.4-2)

NOTE : Please finish the adjustment as soon as possible

4-3. +B MAX VOLTAGE CONFIRMATION

The following adjustments should always be performed when replacing IC651.

1.Supply 230VAC to with variable autotransformer.

2.Input a dot signal.

3.Set the PICTURE control and the BRIGHTNESS controls to minimum.

4.Confirm the voltage of G BOARD TP135V is less than 137.0Vdc.

5.If step 4 is not satisfied, replace IC651 and repeat above steps.

(Fig.4-2)

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