4-2
High Voltage Hold-Down Check
Perform the following checks when replacing the following
components (marked on the schematic diagram).
E board ........ R531, R532, R533, R534, R542, R543,
R544, R545, R548, IC071, IC502, IC531
P board ........ R904, R905, R906
1. Turn OFF the power.
2. Connect the digital voltmeter to the pins 5 and 1 of
CN501 on the E board.
3. Connect a 200 kΩ variable resistor between pins 2 and
1 of CN501 on the E board.
(Maximize the resistance of the 200 kΩ variable risistor.)
4. Set the BRIGHTNESS VR and CONTRAST VR to the
minimum condition.
5. Turn ON the power.
6. Input the dot signal.
7. Check that when the resistance of the 200 kΩ variable
resistor connected to pin 2 of CN501 is gradually re-
duced, the HV protect operated at the following values.
20-inch model: –26.4 to –30.3 V
14-inch model: –23.3 to –26.8 V
8. Turn OFF the power.
9. Disconnect the 200 kΩ variable resistor.
10. Connect the digital voltmeter to the pins 4 and 1 of
CN501 on the E board.
11. Turn ON the power.
12. Input the monoscope signal or all-white signal.
13. Set the BRIGHTNESS VR and CONTRAST VR to the
minimum condition.
14. Check that when the BRITNESS VR and CONTRAST
VR is gradually enlargement, the IK protect operated at
the following values.
Standard Value: –1.44 to –1.56 V
Beam Current Protector Check
Perform the following checks when replacing the following
components (marked on the schematic diagram).
E board ........ R571, IC501
P board ........ R901, R902, R903
BK board ..... R912, R913, IC901
1. Turn OFF the power.
2. Connect the digital voltmeter to the pins 3 and 1 of
CN501 on the E board.
3. Turn ON the power.
4. Input the all white signal or monoscope signal.
5. Set the BRIGHTNESS VR and CONTRAST VR to the
maximize condition.
6. Check the pin 3 of CN501 voltage to –0.94 to –1.05 V.
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