Tektronix 2213 - Page 48

t he Χ - Υ M o d e, ΧΥ Switch transistor Q720 is b iased on to
provi d e α groun d r eference at the other in p ut of the d if-
ferential am p lifier (at the base of Q731) . The output of
the
d
ifferential
amplifier,
taken
from
the
collector of Q731,
is amplifie d by Q736 .
Α feedback network connected b etween the out p ut of
Q736 an d t he b ase of Q730 provides the circuitry required
for the Χ 10 magnification feature . In the unmagnifie d
mode, Χ 10 M agnifier switch S734 is closed and t he feed-
back is provi d ed by the paralleled combination of R732
an d C732 . R esistor R 732 sets the unmagnifie d amplifier
gain an d C732 p rovides the HF compensation .
When the Χ 10 M agnifier push button is pressed in,
S734 opens an d additional components are adde d to the
feedback network . W ith t he fee dback re d uced, the
am p lifier gain is increased by α factor of 10 . The Χ 10 Gain
FR OMΛ S E C/D I V
Χ
SW I TC
H
FR OM I N T ERN AL
X-AXIS
SIG
T R I GG ER
ΑΜΡ
L
HORIZONTAL
P OS I T I ON
R
726
FR O
M
S WEEP
G ENER ATO R
FR OM

BEAM FI N D
Z-AXIS
AMPL
M AGNIF I ER
ΗΟ
R
ΙΣ
Ρ R ΕΛΜΡ
Q730
Q731
Q736
TO C RT
HORIZONTAL
D EFLE CT I ON
PL AT E S
3827-17
ΧΥ Am p lifier
F
igur e 3-7 .
Detaile
db
loc k diag r
am
of t he H o r izo n tal Amplifie r .
Theory of Operation-2213 Service
p otentiometer
(R733) is
ad justed to
produce the exact gain
require d . H igh-spee d linearity compensation
of the feed-
back network is provi de d by a d justable
capacitor C734
.
When t he Χ - Υ display mode is selecte d using the
SEC/
DIV switch, the ΧΥ signal line goes L
O
and ΧΥ Switch
transistor Q720 is biase d off . The ΧΥ signal is also ap p lied
to FET Q714 (use d as α switch to p revent crosstalk) in the
ΧΥ Amplifier to bias it on . W ith t his action, the ΧΥ
Amplifier is enable d to p ass Χ -Axis signals on to the
H orizontal P reamplifier . Another function of the ΧΥ signal
is to d isable the Sweep Generator
to
p revent the Sweep
signal from
being
applied to
the
H
orizontal P
reamplifier
.
The Χ
-Axis
signal is
d
erived from
t he Channel 1 internal
trigger signal and
applie
d to the base of
Q703 . Transistor
3-21