Safety Relatedp Adjustments - Sony KP-48V75 Service Manual

[ G BOARD]
4-1. HV REGULATION CIRCUIT CHECK AND
ADJUSTMENT
When replacing the following components marked with
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)
Fig. 4-1
G BOARD
C514
TP135V
R512
5
IC651
Fig. 4-2
SECTION 4
SAFETY RELATED ADJUSTMENTS
on
Remove the cap off from
the unused terminal and
connect a static voltmeter
there.
– COMPONENT SIDE –
R561
R514
CN505
1
4-2. HV HOLD DOWN CIRCUIT OPERATION
CHECK AND ADJUSTMENT
When replacing the following components marked with
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 130VAC 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)
– 47 –
KP-48V75/53V75/61V75
RM-Y903 RM-Y903 RM-Y903
on