Horizontal Driver; Regulation Circuitry - Wyse WY-120 Maintenance Manual

4-12
Horizontal Driver (5)
Figure 4-12 Horizontal Driver
R202
R203
8
7
IC201
0207
R209
H-Sync
Regulation Circuitry (6)
6
Theory of Operations
The horizontal driver drives the yoke at a given frequency so the
electron beam sweeps from left to right at the correct rate. It also
provides the signal to drive the flyback transformer (Figure 4-12).
A201
+
lC201
R206
5
+
C209l
R212
C210
A211
3 4
C205 C206
T
·fiTC207
VR202
tTl
--~~~-~----------------------------
1"
C208
The regulation circuitry measures the +5 V and +30.S V supplies
(Figure 4-13). It generates an error voltage proportional to any
error it may find when measuring the supplies. Optically coupling
the error signal with the pulse-width modulator that controls its
duty cycle regulates the output voltage of the main switching
power transformer.