Sony TRINITRON KV-20S90, Service Manual, Page: 14 / 94

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KV-20S90 / 21SE43C
HOLD-DOWN READJUSTMENT
If the setting indicated in Step 2 of Hold-Down Operation Confi rmation
cannot be met, readjustment should be performed by altering the
resistance value of R582 component marked with
X .
+
IABL
ABL
T504
FBT
range
-
ampmeter
3.0 mA DC
A
3-2. B+ VOLTAGE CONFIRMATION AND
ADJUSTMENT
Note: The following adjustments should always be performed when
replacing the following components, which are marked with
Y on the
schematic diagram on the A Board:
A BOARD: IC001,IC602, R030, R625, R626,
R632, R633, R635, R636, R637, R638, R639
1. Supply 130 +2.0 / -0.0V to the set with a variable auto transformer.
2. Input a dot signal.
3. Set the PICTURE and the BRIGHTNESS controls to minimum.
4. Set to Service Adjustment Mode.
5. Select PADJ with 1 and 4 .
6. Adjust with 6 to the 0 level.
7. Confi rm the voltage of A Board TP-600 is <125 VDC.
8. If step 7 is not satisfi ed, replace the components listed above, then
repeat the above steps.
9. Supply 130 +2.0 / -0.0V to the set with a variable auto transformer.
10. Adjust with 3 and 6 for 117.0 ± 0.3 VDC.
11. Press MUTING then ENTER to save into the memory.
SECTION 3: SAFETY RELATED ADJUSTMENTS
3-1. X R582 CONFIRMATION METHOD
(HOLD-DOWN CONFIRMATION) AND
READJUSTMENTS
The following adjustments should always be performed when replacing
the following components which are marked with
Y on the schematic
diagram:
Part Replaced ( )
Adjustment ( )
DY, C511, C574, C575, D572,
D573, D574, R582, R583, R584,
R585, R586, R578, R625, R626,
R640, R635,T504, IC301, IC521,
IC602.............................A Board HV HOLD-DOWN
R582
PREPARATION BEFORE CONFIRMATION
1. Turn the POWER switch ON. Input a white signal and set the
PICTURE and BRIGHTNESS controls to maximum.
2. Confi rm that the voltage between C574 (+) and ground is more than
99.8 VDC when set is operating normally with 120 +/- 2 VAC.
HOLD-DOWN OPERATION CONFIRMATION
1. Connect the current meter between Pin 11 of the FBT (T504) and
the PWB land where Pin 11 would normally attach (See Figure 1 on
the next page).
2. Input a dot signal and set PICTURE and BRIGHTNESS to minimum:
IABL = 95 + 100/-95µA.
3. Confi rm the voltage of A Board TP-600 is 117 ± 0.3 VDC.
4. Connect the digital voltmeter and the DC power supply via Diode
1SS119 to C574 (+) and ground (See Figure 1 on next page).
5. Increase the DC power voltage gradually until the picture blanks out.
6. Turn DC power source off immediately.
7. Read the digital voltmeter indication (standard: less than or equal to
127.3 VDC).
8. Input a white signal and set PICTURE and BRIGHTNESS to
maximum: (standard: less than or equal to 127.3 VDC).
9. Repeat steps 4 to 7.