Repair manual

2-63
THEORY OF OPERATION
c. -12V_A Regulated DC Voltage
The -12V_A 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 Negative bias for the Auto Luminance circuit.
o Negative bias for the Vertical Deflection circuit (S-Distortion
Correction, Height, Center, and Driver).
o Negative bias for the COS4 Exposure Correction circuit.
4. CRT Power
The CRT Power is derived from the Monitor P.C. Board flyback transformer and
its associated circuits.
When power is turned on, the logic Controller P.C. Board generates a horizontal
sync signal (MONHS). This sync signal is applied via connector J9 to the input
of the Horizontal Deflection circuit. The Horizontal Deflection circuit processes
this input sync signal and then applies a flyback pulse to the primary winding of
the flyback transformer. The secondary winding of the flyback transformer then
generates the necessary voltages to power the CRT and its associated circuits. In
other words, the voltages are all derived from the output taps of the flyback
transformer.
The particular voltages generated by the flyback transformer are:
o +7 KVDC (Anode Voltage)
o +35 VDC (Cathode Drive Voltage)
o -130 VDC (Auto Luminance - Brightness)
o +850 VDC (2nd Anode and Focus Voltage)
Each voltage and the circuit/circuits that it drives is described in the following
paragraphs.
a. +7 KVDC
This high voltage is used to power the CRT anode. When the Horizontal
Deflection circuit applies a flyback pulse to the primary winding of the
flyback transformer, a high voltage pulse is developed across its