Omron 8025G Maintenance Manual page 70

THEORY OF OPERATION SECTION 4
maintains a constant 5 V dc output with the aid of the current shunt transistor.
Regulated ±12 V dc outputs are produced by T2, a bridge rectifier, and
two voltage regulators. Another section of T2 supplies a 6.3 V ac output as well
as the input voltage to another bridge rectfier that provides an unregulated 80 V dc.
FULL
WAVE
RECTIFIER
BRIDGE
RECTIFIER
BRIDGE
RECTIFIER
, -
REGULA~-l
CARD
IL _____ J
I
I
Figure
4-6.
Power supply block diagram.
+80
v
de
6.3 V de
Circuit Description. Refer to schematic diagrams in Section 8.
o
..
With the terminal on/off switch closed, primary power is applied through
fuse F201 to the fans assembly and to the primary windings of step-down transformer
T2. Power is also applied via fuse F202 to the primary of step-down transformer TI.
One secondary winding (10, 11) of T2 supplies 6.3 V ac for the display CRT
filament via J61-3,4. The 80 V dc output for the 8025 CRT Display is derived from
the voltage across another secondary winding (8, 9) of T2. This voltage is rectified
by bridge rectifier (CR4) and filtered by C4.
Bridge rectifier eR3, connected across the third secondary winding (12, 14)
of T2, is the source for the +12 and -12 V dc supplies.
4-22