Tektronix 434, Инструкция по эксплуатации

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Circuit Description—434
stage does n o t make available a sample o f the Channel 2
signal fo r triggering use. A lso, IN V E R T switch S414 has
been added in the Channel 2 c irc u it. T his sw itch allows the
displayed signal fro m Channel 2 to be inverted.
C H A N N E L SWITCH
General
The Channel S w itch c irc u it determ ines w hether the CH
1 a nd/or CH 2 V e rtica l Preamp o u tp u t signal is connected
to the V e rtica l O u tp u t A m p lifie r c irc u it. In the A L T and
CHOP modes o f ope ra tio n , b o th channels are alte rn a te ly
displayed on a shared-time basis. Fig. 3-4 shows a detailed
b lo ck diagram o f the Channel S w itch c irc u it. A schematic
o f this c irc u it is shown on diagram 3 a t the rear o f this
manual.
Diode Gate
The D iode Gates, consisting o f fo u r diodes each, can be
th o u g h t o f as switches w h ich allow either o f the V ertical
Preamp o u tp u t signals to be coupled to the D elay-Line
D river stage. C R 404, C R405, C R 406, and CR408 c o n tro l
the Channel 1 signal o u tp u t, and C R 410, C R411, C R412,
and C R 414 c o n tro l the Channel 2 signal o u tp u t. These
diodes are in tu rn co n tro lle d by the S w itching M u ltiv ib ra to r
fo r dual-trace displays, or by the V ertical Mode sw itch fo r
single-trace displays.
CH 1. In the CH 1 mode o f o peration, —15 volts is
applied to th e ju n c tio n o f C R411-C R412 in the Channel 2
Diode Gate through V e rtica l Mode sw itch S 45A , R 427, and
C R 433 (see s im p lifie d diagram in Fig. 3-5). T h is forw a rd
biases C R411-C R412 and reverse biases C R 410-C R 414,
since the in p u t to the D elay-Line D river Stage is at about
+6 volts. C R 410-C R 414 b lo c k the Channel 2 signal so it
ca n n o t pass to the D elay-Line D river stage. A t the same
tim e in the Channel 1 Diode Gate, C R 405-C R 406 are
connected to +15 volts through R420. C R 405-C R 406 are
held reverse biased, w h ile C R404-C R408 are forw a rd
biased. T herefore, the Channel 1 signal can pass to the
D elay-Line D river stage.
CH 2. In the CH 2 mode o f operation, the above co n ­
d itio n s are reversed. C R405-C R406 are connected to —15
vo lts through S45E, R 429, and C R 431, and C R 411-C R 412
are connected to +15 vo lts through R425 (see s im p lifie d
diagram in Fig. 3-6). The Channel 1 D iode Gate blocks the
signal, and the Channel 2 D iode Gate allows i t to pass.
S w itching M u ltiv ib ra to r
A L T . In this m ode o f ope ra tio n , the S w itching M u lti­
v ib ra to r operates as a bistable m u ltiv ib ra to r. —15 volts is
connected to the e m itte r o f Q 435 (A lte rn a te Trace
S w itch in g A m p lifie r stage) through R 437. Q 435 is fo rw a rd
biased and supplies c u rre n t to the “ o n " transistor in the
C o m p o s ite
3-6
Fig . 3-4. C h a n n e l S w itc h d e ta ile d b lo c k d ia g ra m .