Tektronix 2235 - Horizontal Preamplifier; X-Y Amplifier

T h eo r y of O pe r atio n -2235 Service
of t he Alternate
Display Switc
h
ing L ogic ci r cuit . See F igure

H orizontal

X10 Gain is set
by
t h
e resisto
r n
etwor k con
3-4 for t h
e bloc
k
diagram of t he H orizo n tal Am p lifie r .

nected between p ins 3 an d 6 . Wh en t h
e

X10
M
ag
n ifier
is on,
S721 is
closed and t
h
e
timi ng
a dju stment is ma d e u si ng
R 754 . M agnifie r registration
is ad j usted b y
R
749 so t h at
T h e Horizontal POSITIO N
co
n
trol, Χ 10 M agnifier circ u it-

t here is no h orizo n tal
trace s
h ift w h
e
n
switc h ing between
r y, and t h e h orizontal p
ortion of t
h
e B eam Find circ u itry are

t h e

X10 M agn ifier
on and
off
positio
n
s .
also con tai n
ed
in t h
e Horizontal Am p lifier circuit .
H
o
r izontal P
ream p lifie r
Th
e
Χ - Υ
Am
p
lifier am p lifies t he C hann el 1 sig n al from t he
T h
e Horizo n tal Preamplifier selects d is p lay mo des and

I n ternal Trigger
ci
r
cuitry fo
r
a pp lication to t he H orizo n tal
am p lifies in p
ut
signals
fo
r
a pp lication to t he Horizontal Out-

Pr eam p lifier .
p ut Am p lifier .
Wh
en
t h
e
Χ - Υ
mode is selected, 0737 is b iase d on to
T he Α and Β Swee p s, selected by U670 B in t h e Alte r nate

esta b lis h α HI on
U760 p
i n 12
so t
h
at t he Α and Β Swee p s
Swee p circuitry, are app lied to t he emitters of 0742 a nd

are disconnected from
t
h
e Pream p lifier outputs . T h e ΧΥ sig-
Q732 respectively t h ro ug h gain pote n tiometers R 740 a nd

ηαΙ line will
b e
L
O and Q756 will be biased off to e nab le t he
R
730 .
T h
e transistors are biased i n to t he active or cutoff

Χ -Axis signal
to
drive
t h e noninverting i npu t of U758 . T he
regions by
t h
e co
n
trol voltage applied at t h e cat hodes of

out p ut of U
758
will
t
h
e
n
be α
f
u nction of t he Χ -Axis sig n al
C
R 732
and C
R
742 . Switch ing b etween t h e Α a nd Β

and t he Horizontal POSITIO
N control wiper voltage . T he Χ -
Swee ps occ u rs wit h in U760, wit h α negative i npu t at p in 10

Axis signal gain
is ad j uste d by R 760 an d t he i npu t voltage
or 9 disconnecti n g t he res p ective swee p from t he r est of t h e

from
t
h
e Horizontal POSITIO N control at p in 14 is d iscon-
amplifier . T h e Horizontal POSITIO N control ad j usts t he
crt

n
ecte d wit h in U760 so t h at it d oes not affect t h e Pream p lifi-
trace positio n t h roug h p in 14 . Out p ut b ias cur r en t levels are

er o u t p ut . T h e i np ut sig n al at p in 11 fr om U758 will be
set b y R 751 at p in 5and fre qu e ncy compe n satio n for Χ -Axis

conve r
ted to α d ifferential outp ut signal an d ap p lied to t he
sig n
als is p rovided by C751co nn ecte d to pi n 13 .

Horizontal
Out p ut Amplifier .
FRO M Α S WEEP

Α S WEEP
G ENER ATO R
S WEEP
FR
O
M
Β SW EEP

Β S WEEP

S W ITC H I N G
G ENER ATO R

Q732
FR
O
M
AL
T ERN AT
E

Α
D I SP

Q742
D I S PLAY

Β ρΙςρ
SW I TC H I NG L OGIC
X-AXIS
X-AXIS
FR O M Α T R I GGER

A MPL
SIG NAL
U758
ΗΟR ΙΖ
PRE A MP
U 76 θ
Χ - Υ Amplifie r
FR O M Α S E C/DI V

ΧΥ

ΧΥ

FR O M

BEAM
S W ITC H
~
E
NABLE

Z-AXIS
F
I ND
8737

A MPL
F ig ur e 3-4 . B loc k d
iag
r
am of t
h
e Ho r izo n tal Am p lifie r .
H
O
R
IZ
O U T PU T
A MPL
ρ 77 θ > Q78 θ
Q775, Q779
Q785, Q789
TO C R T
HOR IZ
D EFLE CT I ON
PLAT E S
42θ 6-11