Tektronix 2235 User Manual

T heory of O p e r atio n -2235 Service
C HA NNEL 2 . For triggeri
ng f r
om C
h annel 2, t h
e
Α
&
Β ΙΝΤ

Sign al current is app lie d to t he emitters of U 350D an d
switc h is set to C H 2 . One
input
eac
h of U555C and U 555D

U 350 E . T he collector curre n t of U 350D is converted to α
will
be
L
O and force
b ot h gate outputs L O . T he L O from

voltage across feedbac k resistor R357 . T he o pp osite-p h ase
U555C will enable t he C
h
a
n nel 2 signal pat h t h
roug
h U 335

collecto r current of U350 E causes α voltage d r op across
and t he HI out p uts of U555
B
and U565C
will
disa
b
le
t he

R 359 w h ic h adds to t he voltage at t he collecto r of U 350C .
C h annel 1 p at
h .

T h is voltage a pp ears at t h e b ase of U350A w h ic h bu ffers
and level sh ifts t he sig n al b ac k to 0 V . T he emitter sig n al of
U350A d rives t h eΧ -Axis Am p lifier, t he Β Trigger Ge n erator,
VER
T M
OD
E . Wh
en
t h e Α &Β ΙΝΤ switc h is set to VER T

a nd t he b ase of U350 B . T h e emitter signal of U350 B in turn
M OD E
,
trigger sou rce selection is determined by
t he two

d rives t h e Α Trigger Generator w henever C R 372 is forward
VER TICA L M OD E switc
h
es .
F
or all
VER TIC AL M
OD
E

b iased .
switc h combi
n
ations excep
t
BOTH-CHOP,
t h e V M ode Τ
line is HI .
T h
e
i n
puts and o
u tp u ts of U555 B , U555C, and
U555D
will
all be HI,
and triggeri ng selection will t hen be
d etermi ned by t he in p uts of U 565 B and U 565C t h at are con -
trolled by
U540A in t he C h ann el Switch circuit .

Α E xte rn al Trigge r Am p
lifier
Wh en C
h
an
n
el
1
is selected ( VER TICA L M OD E switc h
set to C
H 1),
t
h
e
i n
put to U565C will b e HI . T he gate out p ut
will
be
L
O and
t h
e C
h annel 1 signal will
be selecte d .
T h
e L O
from t h e ot h er outp ut of U 540A is applied to U 565 B and
causes t he C h 2 Trig line to go HI a nd t h e C h a nn el 2 Trigger
signal is disabled .
Wh
e
n
C
h
a
nn
el
2
is selected (
VER TICA
L M OD E switc h
set to C H 2), t he o u tputs of U540A, U565 B
,
and U565C will
b e t
h
e reverse of t
h
e states d escri be d for C h annel 1 selec-
tion . T he
C
h annel 2 signal will
be selected and t
h
e C
h
a
nn
el
1 Trigger signal
disa b led .
Wh
e
n
selecti
n g A L T VER TICA
L
M
OD E , t he in p uts of
U565
B
and U565C
will
toggle
wit h
eac
h
swee p . T he outp uts
of t h
e
two
gates
will
also toggle and
t h
e
T r igger sig
n al
source
will alternate wit h t h
e displayed c
h
an
n
el
.
In
t h
e
ADD VER TICA L M OD Ep
osition, b ot h in pu ts to
U565
B
and U565C
will
be HI and
t h
e gate out p uts will be
L O . B ot h C h annel 1 an dC hann el 2 sig n
al
p
at
h
s
will
be
en-
abled and t h ei r output cur r en t will be su mme d
at
t h
e inputs
of t he Inte r nal Trigger Am p lifier to p ro du ce t h
e
internal trig-
ger signal .
T he
C
H O P VER TICA L M
OD
E p osition g r
ounds t
h
e
V M o de Τ line and p laces α L O
on an
in p
ut of b ot
h
U 555 B
an d U555C . T h eou t pu ts of t hese two
gates
will t h
en b e
L
O
and t he sig n al to t he Internal T r igger Am p lifie r will b e t he
same as for t h e ADD mode .
I n ter n al Trigger Am p lifie r
T he Internal Trigger Am
p
lifier co
n
verts t h e d ifferential

Transformer Τ 390 in t h e Power Su pp ly p rovides α line-
trigger sig n als from t
h
e
V
e
r
tical
Pream p lifiers
into α si n gle-

fre qu ency sig n al t h roug h R 397 to Q397 . Diode CR 399 is
ended
sig n
al
t h
at drives
t h
e
Χ -Axis Am p lifier
and
t h
e
Α
and

forwar d b iase d w hen S392 is in t he L I NE p ositio n , and t h e
Β Trigger
Generators .

emitter sig n als of Q397 will d rive t h e Α Trigger Ge n erator .
T he Α External
Trigger Amplifier
buffers
signals a pp lied
to t he ΕΧΤ I NPU T connector to
drive
t
h
e
Α Trigger
Genera-
tor . In p ut signal coup ling is d etermi
n
ed by
Α ΕΧΤ
CO U -
PL I N G switc h S380 w h ic h selects AC, DC, or DC
-
10
coup ling .
Wh en S380 is i n t he AC position, t he i np ut signal is ac-
coupled t h roug h C376 . In t he DC positio n , t he i n put signal is
connected directly to t he Am p lifie r . T he DC
-
10 position
attenuates t he i n put signal b y α facto r of 10 t hr oug h t he
com pensated divider com p ose d of R 377, R378, C380, and
C381 .
T he signal is t hen a pp
lie
d to t he gate of Q382A . T
h
is
source-follower drives emitter-follower transistor 0384
w h ic h lowers t he Am p lifier o u t pu t im pe d ance . T he two FETs
are α matc h ed p air, an d since t he gate and source of 0382 Β
are connected toget
h er,
0382 Β
will
s upp
ly
so ur ce cu rre
n
t
for Q382A
suc
h
t
h
at t
h
ere
will
b e no voltage d ro p across t he
gate-source j u
n
ctio
n
of
Q382A .
Protectio
n -
d io de CR 381
clam
p
s t h e signal at t he gate of Q382A to about -9 V . T he
Am p lifier
o u t p ut will drive t
h
e Α Trigger Generator t h roug h
forward- b iased C R 393
w h
e
n
ever t
h
eΑ SO UR C E switc h is
set to EXT .
Wh
en
t h
e
Α
SOUR C
E switc h
is not set to
ΕΧΤ ,
t h
e base-emitter
j unction
of 0384
will
be reverse b iase d and
t h
e
Am p lifier will
be disabled .
L ine T r igge r Am p lifie r
T h e L ine Trigger Am p
lifier
supp lies α
li n
e-fre que
n
cy
trig-
ger
signal
to
t he Α Trigger Ge n erator w hen t h e Α SOUR C E
switc h is i n t he L I NE p ositio n .

Tektronix 2235 Specifications

General

Brand	Tektronix
Model	2235
Category	Test Equipment
Language	English