Tektronix 2213 - Page 38

C H O P
OSCI L LATO R
U 310C, PIN 8
I NPU T TO
U31 0 B ,
P INS 4 & 5
+5
0
4μ s
3826-23
CH A NNEL 2 SO UR C E .
W hen S305 is set to CH 2, t he
L O logic level present on S305
pin
Β
is couple d to p in Α
an d ap p lie d to U 305D p in 12 and to U 305C p
in
10 . T
he
ou tput of U 305C at p i n 8 is α L Ow
h
ic
h
is a pp
lie d to t he
C H 2 Trig sig n al line by t h e wired-A ND con
n ection .
Wh
en
t h e C H 2 Trig sig n al is LO, t he C han
nel
1 Internal
Trigge r
P ic k off Am p lifier is b iase d off to
prevent t h e
C
hann el 1
signal from reac h ing t he I n ternal
Trigge r Amplifier .
T he inputs to U 305 B , pi n s 4 an d 5, are both pulled ΗΙ
t h ro u g h R 305
an
d R 304
respectively, an d t he ΗΙ outp ut
fr om p in 6, a p plie d to t
h e wire d
-A
N D connection on t he
CH 1 Trig signal
line, allows U 315C to control t he CH 1
Trig signal logic level . As d escribed in t h e prece d i n g "C h an-
n el 1
So
u rce" disc u ssion, t h e logic levels at U 305D p ins 12
F ig ur e 3-4 . CHO P VER TICA L M OD E wavefo r ms .
T h eory of O p e r ation-2213 Se r vice
a nd 13 control t h
e
o u t pu t of U 315 B . T h
e
L O on U 305D
pin 12 en sures α L O ou tp u t at pin 11, w
h
ic
h
is a pp
lie
d to
U 315C at pin 9 . T h is L O ensu res α ΗΙ output at U 315C
pin 8, t h e C H 1 Trig signal line .
W it h t he CH 1 Trig signal ΗΙ , Q273 in t
h
e C
h
an
n
el 2
Trigger P ic k off Am p lifier is b iase d on a n d t
h
e C
h
a
n nel
2
sig n al is passe d on to t h e Inte r nal T r igge r Am p lifier .
VER T M OD E SO UR C E . A dd itiohal switc h settings
are
involve d in d etermining t h e internal t r igger signal selection
w hen VER T M OD E Trigger Source is selecte d . Bot
h
t
he
CH 1-BOTH-CH 2 an d t h e ADD-A L T-C HOP VER TICA L
M OD E switc
h
es establis
h
t
h e vertical sig n al d isplay an d , as
3- 11
THRESHOLD
0
ι
Ι Ι
0 .4 μ s
+5
C HOP BLANKING
PULSE
U 10B, PIN 6
0
+5-9
C
H
O
P
C
L
OC
K
U
317A,
PIN
3
0
Ε
`
+5
C H
1 EN A BLE
U 317A, PIN 5
0
+5
C H
2 EN A BLE
U 317A, PIN 6
0