Dell p780 D99 free download

File name dell p780 D99 chassis-troubleshooting manual.pdf

D99 CHASSIS OPERATION MANUAL TROUBLESHOOTING MANUAL TABLE OF CONTENTS CIRCUIT DESCRIPTION D Board (Power Supply Section) ... 2 D Board (Deflection Section) ... 9 A Board ... 20 GENERAL TROUBLESHOOTING ... 26 PARTS LEVEL BOARD REPAIR ... 37 TRINITRON® COLOR COMPUTER DISPLAY -1- CIRCUIT DESCRIPTION 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 topology is a discontinuous mode flyback converter with 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 Secondary Circuitry Protection Circuits Troubleshooting The power supply has four modes of operation, `off', `active off', `suspend/standby' 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 1 Failure 2 Failure 3 Aging/Self Test Syncs N/A No H and V No H or V H and V Present NA NA NA No H and V Condition Power 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 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 Except for power switch off, all modes of operation are controlled by the microprocessor located on the D Board. The failure modes are detected by the microprocessor and the power supply is forced into active off mode. These functions are discussed later (Deflection). With the AC cord attached to the monitor and connected to an AC source, the monitor will be off until the power switch is turned on. When the power 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/standby modes. Heater On/Off is digital low for active off mode. 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 B+ 80V +15V -15V +12V 5V H eater H . C entering ST B Y 5V Off 0V 0V 0V 0