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D BOARD POWER SUPPLY SECTION
Power Supply Electrical Circuit
The power supply is located on the D Board. It has three modes of operation that are controlled by a microprocessor. The
architecture is similar to discontinuous mode flyback converters and has photocoupler feedback for regulating the secondary
voltages. Circuit operation and troubleshooting are explained in the following sections:
Operation Modes
AC Input
Degauss Circuit
Primary Circuitry
Operation Modes
The power supply has four modes of operation, 'off', 'active off', 'suspend' and 'active on'. These modes are related to
power savings and are indicated by the front panel LED. Additional indications are failure diagnostics and aging mode.
The table below lists operation mode, condition and LED status.
Mode
Off
Active Off
Suspend/ Standby
Active On
Failure
Failure 2
Failure 3
Aging/Self Test
Except for AC switch off, all modes of operation are controlled by the microprocessor located on the N Board. The failure
modes are detected by the microprocessor and the power supply is forced into active off mode. These functions are dis-
cussed later (Deflection).
With the AC cord attached to the monitor and connected to an AC source, the monitor will be off until the AC switch is
turned on. When the AC switch is turned on, the power supply starts and is in active off mode. The next step is active on
mode. The power saving modes are activated by the microprocessor based upon the presence of either H or V sync. If no
sync signals are present, the power supply is set to active off mode. If only horizontal sync is present the power supply
moves to suspend mode. If only vertical sync is present the power supply enters standby mode.
Power supply operation control signals are "Remote On/Off" and "Heater On/Off". Remote On/Off is digital low for active
off and suspend modes. Heater On/Off is digital low for suspend mode. Suspend mode is similar to active off mode, but
with heater voltage on. To enter active on mode, the microprocessor must set remote on/off to digital high. Heater on/off is
also made digital high and the heater is turned on.
Output
± 16.5V
-16.5V
Heater
H. Centering
CIRCUIT DESCRIPTION
Secondary Circuitry
Protection Circuits
Troubleshooting
Syncs
NA
No H and V
No H or V
H and V Present
1NA
NA
NA
No H and V
Off
B+
0
8 0 V
0
0
0
+12V
0
5 V
0
0
0
Condition
AC Switch Off
Low Power, Heater Off
Low Power, Heater On
Phase Locked, Normal Operation
HV or +B Failure
H Stop, V Stop, Thermal Failure
ABL Failure
Aging Raster or Test Pattern
Active Off
Suspend
120V
120V
5 5 V
5 5 V
8.7V
8.7V
-12V
-12V
0
0
+5V
+5V
0
3.2V
± 5 V
± 5 V
-
2
-
LED
Off
Amber
Amber 0.5s<- ->Green 0.5s
Green
Amber 0.5s<- -> Off 0.5s
Amber 1.5s<- -> Off 0.5s
Amber 0.5s<- -> Off 1.5s
Green 0.5s<- -> Off 0.5s
Standby Active On
180V
7 8 V
+16.5V
-16.5V
+12V
+5V
6.3V
± 8V
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Troubleshooting
