BELINEA 10 55 70, Service Manual

Page: 32 / 80

(a) Second half of scanning period
(b) First half of return line period (t2
(c) Second half of return line period
(d) First half of scanning period
Figure 3-21 Polarity of Transformer Voltage
The voltage seen in the output stage require
special attention. The B+ supply can varying
between 60-180. The main
pulse seen
across 4301 and associated components is
around 1200V. Consequently. appropriate pre-
cautionary measures must be taken when serv-
icing the monitor.
In addition to the basic’topology as described
above, there are a number of other additional
devices.
4303 and can be inde-
pendently turned on or off under logic control.
These devices switch addition capacitors,
C313, C324 and C328 in parallel with
to
alter the amount of ‘S’ correction at different
Figure 3-22 Basic Horizontal Output Circuit
P a r a b o l i c
horizontal scan ferquencies.
D308 and D309 set up a positive and a negative
supply rail with respect to the main B+ supply.
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
current into This flows into the
deflection yoke and adds a variable DC offset
to allow
raster entering to be achieved.
The B+ supply is configured so as to maintain
a constant voltage. The anode voltage is
derived from transformer, T302. As
the across primary is al-
ready a high of around it
requires only a modest turns ratio to this
pulse up to around the working
of the CRT.
Figure 3-23 Linear Ramp Distortion
VDM. This voltage is derived from the output
of Q353 after buffering by a unity voltage gain
amplifier formed by Q354 and Q355.
.
The pulse at the primary of T302 is
proportional to the both frequency and sup-
ply rail, B+. In order to maintain the anode