Service manual

ViewSonic Corporation Confidential - Do Not Copy VA702-3_VA702b-3
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Oscillator with an active current sense circuit. Desired output voltage are determined by the equation,
Volt = 1.25 ( 1 + R67 / R66), In this case, the output voltage are 3.3 Volts
The AIC1739 is a low dropout positive adjustable regulator with minimum of 300mA output current capability.
So it is well suited for 3.3 V and 2.5 V Regulator.
6.1.3 Power Regulator MC34063A (U7) : The MC34063A is a monolithic control IC containing the primary functions required for DC
to DC converters. The device consists of an internal temperature compensated reference, comparator, controlled duty cycle.
Oscillator with an active current sense circuit. Desired output voltage are determined by the equation,
Volt = 1.25 ( 1 + R85 / R86), In this case, the output voltage are 5.0 Volts for panel power.
6.2 Power(Inverter) Board
This is a specific power(inverter) power board for VA702-3 monitor 40W 12V 3.5A output power and backlight which
converters 12 Vdc to drive four cold cathode fluorescence tubes.
6.2.1 Inverter Electrical specification described as below.
Rated Input Voltage 12Vdc
Input Voltage Range 11.4 ~ 12.6 Vdc
Input Current <2A
Input
On / Off control Voltage 2~3.3 for on , 0~1 for off
Rated Output Strike-on Voltage 1500Vrms
Rated Output Voltage 710Vrms at 7mA
Rate Output Frequency 40~50KHz
Output
Rated Ourput Current 7~8 mA
6.2.2 power
This is a general purpose AC / DC adapter which converter 90~240 Vac to a stabilized DC voltage 12 V with rated output
current of 4.16A . Electrical specification described as below.
Rated Input Voltage 90~240 Vac , 50 / 60Hz
Operation Input Voltage 90~260 Vac , 47 ~ 63Hz
Input Current <1.5A
Inrush Current <100A@120Vac
Standby Input Voltage 12Vdc
Output Voltage Regulation +/-5%
Output Ripple & Noise 120mVp-p
Rate Output Current <3.5A
Turn-on delay <3secs