Repair manual

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THEORY OF OPERATION
3. DC Power
As previously stated, the Monitor P.C. Board contains all the necessary electronic
circuits to process the digital video signals and to drive the CRT.
DC power to operate its electronic circuits and to drive the CRT is supplied by
the Power Supply Module. Refer to Section C in this Service Manual for detailed
information on how the Power Supply Module distributes regulated DC power to
the Monitor P.C. Board. The Power Supply Module supplies the following
regulated DC voltages to the Monitor P.C. Board:
o +12V_A (+12vdc)
o +12V_B (+12vdc)
o -12V_A (-12vdc)
The following paragraphs describe the function of each of the regulated DC
voltages that are applied to the Monitor P.C. Board by the Power Supply Module.
a. +12V_A Regulated DC Voltage
The +12V_A Regulated DC Voltage is supplied via connector J3 on the
Logic Controller P.C. Board and connector J9 on the Monitor P.C. Board.
This regulated DC voltage is used for the following:
o Positive bias for the Horizontal Deflection circuit (Center, Width, and
Linearity).
o CRT heater filament.
b. +12V_B Regulated DC Voltage
The +12V_B Regulated DC Voltage is supplied via connector J4 on the
Logic Controller P.C. Board and connector J9 on the Monitor P.C. Board.
This regulated DC voltage is used for the following:
o Positive bias for the CRT Cathode Driver circuit.
o Positive bias for the Auto Luminance circuit.
o Positive bias for the Vertical Deflection circuit (S-Distortion
Correction, Height, Center, and Driver).
o Positive bias for the COS4 Exposure Correction circuit.