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Product:
see llst
date:2-22-88
Chg. Ref:
M6391r
Replace
the
description
for
the Deftection
Amptifiers
(Diagram
27)
with
the
tottowing.
DEFLECTION
AMPLIF|ER
(Diagram
278)
Refer
lo ihe
block
diagram
adjacenl
to Diagram
27
as
well
as the schematic diagram. The
Deflection
Amplif
ier
receives
verlical
signal inlormation
trom
the vertical
section of lhe Digital
Storage of the
Video
Processoi,
and
horizonlalorsweep
board.
The
Readoul
data forthe
display comes
tromthe
CR1 Readout
circuits. The
output
of
the Deflection
Amplifier
drives
the
crt
dellection
plates.
The
amplitiers contain
lhe switching
circuits
necessary
lo
perform
the selection
functions
and
they
also contain the amplifier
stages
needed
to
product
the
defleclion
plate
drive
signals.
Horizontal
Section
Signal
lines
HORIZONTAL
SIGNAL (from
lhe digitatstorage
circuits through
edge connector
pin
49)
and
Sweep
(from
the
Sweep
circuit
through
edge
connector
pin
51)
are
apptied
to switCh
U7O55A. U705s,
under
conlrolof
the
STORAGE
OFF
signal
(from
the
digitalstorage
circuits
through edge connectorpin 7),
setects
eitherthe
HORIZONTAL
S|GNALorSWEEPinput.
The
SWEEP signatis setectedwhenthe
STORAGE
OFF
line is
pulled
low.
Resistive
divider
R7065
and R7070 reduce
the selected signal
trom
1V/div
to o.Sv/div.
U7073
buff
ers the
selected
signal.
The
sefected
signal
goes
out to
the
HORTZ
OuT
rear-panet
conneclor
via
pin
1
and 2
on
P6100,
P6090
and
pin
48
of
the edge connector.
U7073 appties
the signat
to switch
U70558.
The
HORIZ
R/O
OFF
signal, trom
the
Crt
Readoul
selects between
these two
signati.
When
R/O is floating
or
pulled
high,
the
switch
transmils
the signal lrom
buffer
U7073 to
lhe shaper.
When
the
tine
is
puled
tow,
it
selects
the
HORIZONTAL
R/O
signat.
U7055
applies
the
signal
to
a shaper
network
lo compensate lor non-linearity
in
the crt deflection
characteristics.
This
network
consisls
of
resistors
R5059,
R5058, R50S7,
R4061, iaosg,
and
R5062,
plus
diodes
CR4052,
CR4051
,
CR4958,
and
CR4056. The
HORIZONTAL POStTtON
vottage,
from
the
f ront
panel
via
edge
conneclor
pin
47,
through
resistor
R5056,
is
applied to the shaper circuit
so tne
shape conection
lactor
relates
lo
the
crt deflection.
The
shaped
signal
is
then
applied
lhrough
preamplifier
U2055 to
the def
tection
amplitier circuits. HORTZ
gain
adjuslment
R1055,
calibrates
lhe
amount
of
gain
compensation required for
proper
deflection
sensitiviiy.
The
horizontal
detlection
amplilier
consists
of two circuits
similar to each other, one
for
each
horizontal
deflection
plate.
One
circuit
is
an
inverting
amplitier,
the
other
operates
in-phase.
Inputs
to U2030
of the
inverting
side
are
through
the
paraltel
combination
ol
resistors
R1
039 and R1038
and capacitor C1040. The
series
conneclion
of
resistor
R1038
and
variable
capacitor
Cl040
provides
high-frequency response
compensatio
n -
capacit
or
c2047
controts
high{requency
f
eedback.
fnpul
lo
lhe
non-inverting
side
of the
amplifier is
through resistor
R1025 to
u2030.
R1o?'zand
R2020
set
the
dc level
for
the feed-back
loop
to
the
plus
input
side of the
amplifier.
Variable
capacitor
C1030
provides
adjustment
to
sel
lransient
gain.
High
frequency
feedback
is
controlled
by capaciior C20tO.Gain
ol each
amplifier
section is
approximately
20.
(Horizontaldellection
sensilivityof
lhe crt
is
approximately
21.3v/div
per
side.)
Signalswith
a
low
rate
of
change
drivethe
oulput FETtransistorsthrough
R3038,
asthe
rate
ol
rise
increases,
the
drop
across
R3040
increases
and when
it
reaches
0.6V,
either 03047
or e3046 biased
on.
These
transislors
provide
high
current
drive for
the
output
lransislors. When
the signal
rate
ol change is low, 04030
drives
the
crt defleclion
plates
and
Q4040
provides
bias currenl
for
the amplitier,
As
the
rate
or
rise
increases,
949?1
couples
the
signalto
the
gate
of 04040.
04040
provides
the
posilive
drive to the
deflection
ptate,
and
04030
provides
the negative
drive. Each
output
transislor
can
provide
a 200V
excursion
in
approximately
1
ps.
Page
3
of 5