Sony KP 48S75 - Manual (Page 47)

– 47 –
KP-43T75/48S75/
53N77/53S75/61S75
RM-Y906
Remove the cap off from
the unused terminal and
cpmmect a static voltmeter
there.
SECTION 4
SAFETY RELATED ADJUSTMENTS
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 necessary re-adjust.
: C517
: C517, C521, C522
IC654, L504
T502, T504 (FBT)
D.Y, A board, G board
[ G BOARD]
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.
: R536, R545
: C516, C536
D506, D507, D522
IC206, IC502, IC654
L504, R511, R522, R536, R538, R545,
R548, R584
T502, T504 (FBT)
D.Y, A board, G board
Fig. 4-1
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 ± 1.0 kVdc. 1.5
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 31.95kV or higher, replace C517 of 470PF/
2kV with that of 1000PF/2kV, and check if the voltage is
within the standard range.
5. If anode voltage is 29.45kV or lower, replace C517 of 470PF/
2kV with that of 100PF/2kV, and check if the voltage is within
the standard range.
OPERATION CHECK
4-3. +B MAX VOLTAGE CONFIRMATION
The following adjustments should always be performed when
replacing IC654.
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 IC654 and repeat above steps.
HV HOLD-DOWN ADJUSTMENT
1. Repart steps 1 ~ 7 as above.
2. If hold down voltage is 34.5kV or higher, remove R536,
mount a resistor (150k Ω , 1/4W : RN) onto R545 instead, and
check again if the hold-down voltage is within the standard
range.
3. If hold down voltage is 32.5kV or lower, mount a resistor
(220k Ω , 1/4W : RN) onto R536 and check again if the hold-
down voltage is within the standard range.
NOTE : Please finish the adjustment as soon as possible
1. Remove CN652 connecter.
2. Short-circuit across TP-PROT and ground.
3. Connect a HV static voltmeter to the unconnected plug of
the high-voltage block.
4. Connect a 220 Ω /200W variable resistor, across pin 2 and
pin 1 of CN652 and connect an external dc power supply
unit (200V, class 2A) to pin 3 of CN652.
5. First turn on the external power supply (+B=135V), then
turn on the power of the set.
6. Receive the dot signal. (PICTURE and BRIGHTNESS to
minimum)
7. Gradually increase the value of the external dc power supply
and check that the hold-down circuit operates at a static
voltmeter reading of 33.5
± 1.0kVdc when the raster
disappears.