BELINEA 10 55 70, Service Manual

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(a) Second half of scanning period (tl
(b) First half of return line period t3)
I
(c) Second half of return line period
(d) First half of scanning period (t4 t5)
Figure 3-8 Polarity of Transformer Voltage
current
into current flows into the
deflection yoke and adds a variable DC offset
to allow image raster entering to be achieved.
The B+ supply is configured so as to maintain
a constant anode voltage. The anode voltage
derived from the transformer, As
the voltage across the primary is
ready
a high voltage pulse of around it
requires only a modest turns ratio to step this
pulse up to around the working voltage
of the CRT.
Figure 3-9 Basic Horizontal Output Circuit
P a r a b o l i c v o l t a g e
o v
amp
- -
The pulse at the primary of is
proportional to the
both
frequency and the
ply rail, B+. In order to maintain the anode
voltage at a constant 26kV a regulation system
is required. This is achieved
using a buck regu-
lation stage formed by a driving a
synchronized by the horizontal oscillator. The
has an error amplifier that generates an
error signal from the feedback network formed
by the high voltage bleed resistor (it is internal
to
Resistors RP14 and RP13 set
the DC feedback ratio, and by adjustment of
VRP this ratio can be adjusted at to set
the high at it’s nominal of 26kV.
AC of loop
is set by CPI 1 and RP21 for optimum stability
and relegation
Figure 3-10 Linear Ramp Distortion
Q352 acts as a constant current source that can
be programmed under logic control. This
cur-
rent source drives the transistor pair and
which thus drive an adjustable constant
The output of error which can bc
observed on ICP2 of pin 5 is com-
pared with a DC voltage. This DC is produced
across.
CP4, charge by The voltage across this
capacitor is periodically discharged by
which is fed by a pulse from the horizontal