Hitachi 46W500 Training page 11

DP-3X LED (Visual Trouble Detection) CIRCUIT EXPLANATION
This explains the LEDs used in the Deflection Power Supply used for Visual Trouble Shooting Circuit Dia-
gram explanation:
(See DP-3X LED (Visual Troubleshooting) for the Deflection Power Supply Diagram for details)
5 LEDS, 4 GREEN AND 1 RED
In the DP-3X chassis, there are 5 total LEDs that can be used for Visual Trouble shooting. 4 Green and 1 Red.
Use these LEDs to determine if the set is experiencing a problem.
The LEDs can be used in the following ways.
OFF:
If the LED is off, then the power supply that is being monitored is unavailable. (Excluding the possibil-
ity that the LED itself is malfunctioning). NOTE: If D932 LED opens, then the set will be in shut down
condition because of it's current flow explained below.
If the LED turns on but then quickly goes off before the others, then the power supply that is being
monitored can be suspected.
ON:
If the LED is on, then the power supply that is being monitored is working normal. (There is the possi-
bility that the power supply being monitored may in fact be present but low. If after making visual in-
spection and all seems OK, but there's still a problem, be sure to check the accuracy of the power supply
in question.
RED LED D912
D912 is used to monitor the Start Up and Run voltage for the Driver IC I901. This IC is used to generate the fol-
lowing voltages.
•
Audio SW +30V
•
SW +10V
•
+220V
•
SW+28V
•
SW -28V
•
SW +115V
The LED D912 is attached to pin 4 of I901. If the voltage is missing, the LED will not light.
GREEN LEDs D956, D955, D954 and D932.
D956 (Audio +30V)
•
Monitors the Audio +30V output from T901 pin 18 and rectifier D919 cathode.
D955 (SW +5.5V)
•
Monitors the SW +5.5V generated by the SW +5.5V regulator I905 pin 1 from T901 pin 15 and rectifier
D922 cathode.
D954 (SW +28V)
•
Monitors the SW +28V output from T901 pin 15 and rectifier D922 cathode.
•
Note: This LED requires the SW –28V power supply to be functioning to operated. If the LED opens, or
the negative SW –28V is missing, this LED will not illuminate. If the SW –28V is missing, the set will
shut down.
D932 (SW +115V)
•
Monitors the SW +115V output from T901 pin 11 and rectifier D925 cathode.
•
This power supply is used for Deflection and High Voltage generation.
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