Tektronix 7704A User Manual

Circuit Description
-7704A
Service
H O R IZO NTA L A
MPL I F I ER
T he H orizontal
Amplifier circuit amplifies t he push-pull
h orizontal deflection
signal from t he H orizontal Interface
circ u it and connects it to t
he h orizontal deflection p lates of
t h e C RT . T h is circuit also
receives t h e Χ Readout signal
from t he Rea d out System
to p roduce t h e h orizontal
portion of t
he readout display . F ig u re 2-47 s h ows α detaile d
b lock d iagram of t h e H orizontal Amplifier circuit .
In put Am p lifier
T he horizontal signal from t
he H orizontal Interface
circuit is connecte d to t
h e
b ases of
Q4321 an d Q4331 . T he
gain of t
h
is stage
is controlle d by t h e resistive networ k
between t h e emitters of Q4321-Q4331 . H orizontal Gain
ad j ustment R4310 is variable to set t he overall
gain,
an
d
t h ermistor RT4313 p rovi d es t
h ermal gain com pensation . As
t h e tem p erature goes up,
t he resistance of RT4313 goes
down, resulting
in
less
emitter d egeneration . T h erefore, t he
overall gain increases to
com pensate for t he opposite
temperature c h aracteristic of
t he transistors in t h e H ori-
zontal Amplifier
circuit
.
Transistor
Q4304 normally supplies most of t h
e emitter
current of Q4321-Q4331
. H owever, w h en t
he BEAM
F I N DER switc h is
actuated, Q4304 is no
longer forward
b iased so t h e
current t h roug h R 4307-
R
4309 is
determine d
by R4304 only .
T h is results in less
current to Q4321 an d
Q4331, so t h eir d ynamic range is
limite d . T h is reduces t he
effective gain of t he h orizontal
system to kee p t he d isplay
2-58
LEF T O U T PU T
A MPL I F I ER
R IG H T OUT PU T'
A MPL I F I ER
Q4535, 04
4361
390
Q4395
INPU T A MPL I F I ER
Q4304, Q4321
Q4331
F ig . 2-47 . H orizo n tal Am p lifie r circu it d etaile d
b loc k d iagra m .
with in t h e h orizontal limits of t
h e graticule, regardless of
t h e setting of t
h e h orizontal p ositioning controls or t he
h orizontal
signal amplitu d e .
H orizontal Centering ad j
ustment R4325 provides
ad j ustment for d ifferential
un
b
alance in t h e H orizontal
Am p lifier circuit . T he limiting
networ
k
CR 4323-C R 4333-
C R 4340-C R 4342 limits t
h
e
inp u t to t h e succee d ing
stages, so t h ey always op
erate wit h in t h eir d ynamic
range and
are not overdriven by excessive
current
from t h e In put
Amplifier stage . Since t h e output
from
t
he
In put Am p lifier stage
is α current signal, very little voltage
c h ange occ u rs across t
h e limiting networ k . Wh en h orizontal
d eflection signals t h at p roduce an
on-screen display are
ap p
lied, CR4323 an d C
R4333 remain forwar d biase d and
CR 4340-C R 4342 are
reverse biase d . H owever,
if h ig h -
amplitu de signals are
applie d to t h is circuit as α
result of
sweep
magnification or external signals,
eit h er C R 4323 or
C
R 4333 is reverse biase d , depen d
ing
on
t h e polarity of t h e
overd rive signal . T h is results
in
α
sufficient voltage ch ange
at t he anode of eit
h
er
CR4340 or CR4342 to forwar
d b ias
it . T h e s hun t d io d
es provid e α current p at
h
for
t he signal
current to
limit t he current ch ange at t
he bases of
Q4325-Q4335
du ring t h e overd rive con d
ition .
For rea d out displays,
t he Χ Rea d out signal from t h
e
Reado u t System is
connecte d to t he base of Q4321 t
h
roug
h
R 4300- R4322 .
T he signal from t he h orizontal
plug-in units
is bloc k
e
d
in t he H orizontal Interface
circuit so t h e
Readout
System p rovides t h e only
h orizontal deflection .
Q4321 an d
Q4331 operate as α parap
h ase am p lifier to
convert t
he single-ende d rea d out signal at t
he base of
Q4321 to
α push-pull signal at t h e
collectors of b ot h Q4321
and
Q4331 .
HORIZONTAL D
EFLE CTIO N
SIG N A L ΤΟ
R
IG
HT
D EFLE CTIO N PL AT E
O F CRT
55007 Β Q43'25, Q4351
Q4356,Q4371
BEAM F I N D ER Q 43 β Ι
Owl
HO R
IZO N
TA L
DEFLECT ON
SIG N AL TO LEF T
N OW
DEFLE CTIO N PL AT
E
OF C R T
χ RE ADO U T SIG N AL
FR O M RE ADO U
T
SYST Ε Μ T HERM A L
B A L ANCE
ΗΟ R ΙΖΟΝΤΑί SIG N AL= NE
T W
O
RK
FR O M HOR IZO N TAL
Q
434G
I NT E RFAC E CIRCUIT

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English