Genius 2093 Manuale Utente
The diode modulator controls the horizontal yoke
current which affects the horizontal size. This is
accomplished by the diode forward current. In effect,
the diode shorts out the horizontal width coil to the
extent of the diode forward current during the previous
horizontal trace time. The current used to control the
diode forward current comes from the diode modulator
and is controlled by the control circuit and the
switching mode driver.
current which affects the horizontal size. This is
accomplished by the diode forward current. In effect,
the diode shorts out the horizontal width coil to the
extent of the diode forward current during the previous
horizontal trace time. The current used to control the
diode forward current comes from the diode modulator
and is controlled by the control circuit and the
switching mode driver.
HORIZONTAL RASTER WIDTH CONTROL CIRCUIT DESCRIPTION.
The beam current from the FBT is converted to a
voltage by resistors
voltage by resistors
009
and is filtered by capacitor
010
. Resistor
097
then connects the signal to the
current node of the control amplifier, which
accomplishes the blooming correction function.
accomplishes the blooming correction function.
The horizontal size voltage from the remote control
PCB
PCB
490
is applied directly to the current node
(LM392 Pin 5) of the control amplifier by resistor
043
.
The horizontal width control circuit is comprised of
two main parts; The control circuit and the diode
modulator (DM). The control circuit combines four
signals in the monitor to produce the width control
circuit. These signals are:
two main parts; The control circuit and the diode
modulator (DM). The control circuit combines four
signals in the monitor to produce the width control
circuit. These signals are:
3. Correct horizontal raster distortion caused by
periods of high beam current.
periods of high beam current.
2. Correct pincushion distortion in the vertical axis.
1. Provide a convenient means for adjusting
the horizontal raster size.
the horizontal raster size.
The purpose of the horizontal width control is to:
4.
EHT return on the FBT
Vertical yoke return.
3.
V. current feedback resistor
2.
H. Size Pot.
1.
Beam current - - - - - - -
Vertical parabolic + Iv
Vertical current (Iv) - -
Horizontal size - - - - - -
For pincushion correction, two separate signals are
used. The inverted vertical current waveform
(TP 34) and the yoke return waveform (TP 33). The
yoke return waveform includes a parabolic and linear
component. The inverse of the linear component is
added to the yoke return waveform to correct the
pincushion. The vertical current waveform (Iv) is
inverted by an Op Amp and resistors
used. The inverted vertical current waveform
(TP 34) and the yoke return waveform (TP 33). The
yoke return waveform includes a parabolic and linear
component. The inverse of the linear component is
added to the yoke return waveform to correct the
pincushion. The vertical current waveform (Iv) is
inverted by an Op Amp and resistors
029
and
051
.
Resistor
031
level shifts the inverted Iv to + 6V.
The (vertical parabolic + Iv) is AC coupled by capacitor
082
and resistor
038
and
040
. It is then
amplified by an Op Amp connected as a voltage
follower. Resistor
follower. Resistor
038
protects the Op Amp against
arc related voltage spikes. Load resistors
050
and
053
prevent cross over distortion of the Op Amps by
using only the current source transistors.
The inverted Iv and (parabolic voltage +Iv) are added
to the current node of the control amplifier by resistors
The inverted Iv and (parabolic voltage +Iv) are added
to the current node of the control amplifier by resistors
041
,
042
,
030
, &
052
which then makes up the
pincushion correction signal.
The power output stage of the horizontal width
control circuit is a high efficiency switching mode
driver. The FBT pulse is integrated by capacitor
control circuit is a high efficiency switching mode
driver. The FBT pulse is integrated by capacitor
057
through resistor
095
and level shifted by resistor
058
to produce a saw tooth waveform. See waveform block
TP 39. By connecting one input of the comparator, in
the LM392
TP 39. By connecting one input of the comparator, in
the LM392
049
, to this sawtooth signal and the other
input to the control amplifier a switched signal with a
duty cycle dependent on the control voltage is
produced at the output. Resistors
duty cycle dependent on the control voltage is
produced at the output. Resistors
055
and
056
form
a voltage divider which limits the control voltage
amplitude to be within the sawtooth waveform.
Resistor
amplitude to be within the sawtooth waveform.
Resistor
060
acts as a pullup for the comparator
output. Resistor
461
couples the power MOSFET
460
to the comparator. Capacitor
463
and resistor
464
are connected as a snubber circuit to reduces noise due
to rapid drain transitions.
to rapid drain transitions.
When the MOSFET is on (gate voltage high)
current increases in inductor
current increases in inductor
458
and when the
MOSFET is turned off the current is dumped in to the
24-27V line through diode
24-27V line through diode
462
. The magnitude of
this current, from the diode modulator, is determined
by the duty cycle of the MOSFET which is a function
of the control voltage.
Diodes
by the duty cycle of the MOSFET which is a function
of the control voltage.
Diodes
477
and
478
with current equalizing
resistors
475
and
476
rectify the flyback waveform
present on the GND referenced node of the
horizontal tuned circuit. This current is conducted
through inductor
horizontal tuned circuit. This current is conducted
through inductor
457
and integrated by capacitor
456
and then is controlled by the driver circuit.
Diodes
477
and
478
are the diode modulator
diodes and the forward current which the drive
circuit controls is the current which determines the
turn on delay of the GND referenced node of the
horizontal tuned circuit. An increase in the current
of diodes
circuit controls is the current which determines the
turn on delay of the GND referenced node of the
horizontal tuned circuit. An increase in the current
of diodes
477
and
478
produces a greater delay in
the GND referenced node, and reduces the amplitude
of the flyback pulse at this node, which results in an
increased horizontal size.
of the flyback pulse at this node, which results in an
increased horizontal size.
Capacitors
441
and
442
are the primary
horizontal tuning capacitors and must be the specified
value for a given chassis horizontal frequency and
yoke combination for proper operation of the monitor.
Capacitors
value for a given chassis horizontal frequency and
yoke combination for proper operation of the monitor.
Capacitors
437
and
439
are the diode modulator horizontal tuning
capacitors. Diodes
440
and
438
clamp the GND
referenced node voltage to GND. Horizontal linearity
coil
coil
431
stores energy from the flyback pulse and
injects it into the horizontal yoke in the reverse
direction of the yoke current to decrease deflection at
the start of trace to balance the decreased deflection at
the end of the horizontal trace due to I R losses in the
yoke during trace time. Capacitor
direction of the yoke current to decrease deflection at
the start of trace to balance the decreased deflection at
the end of the horizontal trace due to I R losses in the
yoke during trace time. Capacitor
432
and resistor
428
keeps the linearity coil from ringing after retrace.
The raster may be shifted by making solder
connections: left
connections: left
SL
or right
SR
. The amount of the
shift is set by solder connections
S1
,
S2
, &
S4
.
Inductor
447
permits only the DC current to pass to
the yoke return. Resistors
423
,
424
, &
425
define
the size of the shift together with the V+ plus 5V and
V+ minus 5V supplies. Resistor
V+ minus 5V supplies. Resistor
189
supplies a load
on the V+ ±5V lines to avoid over-voltage of the filter
capacitors. Resistors
capacitors. Resistors
185
,
195
act as fuses to protect
the PCB in the case where both
SL
and
SR
connections are made.
These circuits are designed around a virtual ground,
the +6 volt line. This line is generated by buffering a
voltage divider
the +6 volt line. This line is generated by buffering a
voltage divider
022
and
023
with an OP Amp.
Resistor
021
and capacitor
026
form the output filter.
490
2
029
051
031
040
038
038
082
050
053
041
043
042
030
052
009
010
097
095
058
055
056
460
464
463
461
060
049
458
462
457
456
441
442
440
438
431
432
428
447
423
424
425
185
195
189
057
S1
S4
S2
SL
SL
SR
SR
84
022
023
026
021
437
439
477
478
475
476
477
478
477
478