Technics ST-9030 - Technical Description; IF Wide Narrow Automatic Change over Circuit; Wide Narrow Switching Circuit

E
TEC¡-INICAL
DESCR¡PT¡ON
ô
rF
WIDE-NARROW
ortororia
ãro*ar.QVER
CrRCUrr
[Fig.
1j
":
'
O
Functions
of TR410,
TR414
and
TR415
of
muting
circuit
(During
tuning)
ÏR410
is
turned
"oFF"
during
tuning,
with
positive
poîentiar
appearing
ai
the
coilectoi.
(Refer
to
the
¡tem
4
of
ihe
mut¡ng
circuit
operating
principle
description).
vvr¡vv\v¡
\¡
¡vre¡
Since
the
collector
of
rR41o
is
connected
to
the
base
oÍ
TB414,tile
sâme
positive
potentiel
is
also
applied
tc the
base
oí
TR414'
Meanwhíre,
positive
vortage
ror¡¡er
than
the
power
source
volîage
by
approximately
0.ôV
is
ap-
plied
through
the
siiicon.diode
D407
to
the
emitler
oíTR414,anc
therefore,
tr'¡r
tr.^i.i*
"ir*,
,uo.
is
turned
"oFF"'
with
negative
potential
appearing
at
the
collecror.
Thus
TR4ls
is rurned
,,oN,,by
th¡s
negati,/e
po-
tentiar,
and
the
coilector
of
rR4
1
5
is rendered
to be
of
ground
ootenliar.
(During
detuning)
TF410
is
turned
"oN"
during
detuning.
with
the
collector
rendered
to
be
of
ground
potentiaí.
Thereafter,
TR414
isturned
"oN",w'hileTR4lsisturned"oFF"inthereverseorderrothatduringthetuning.
According-
ly, negative
potential
is
developed
at
the
collector
of
TR4
j
5.
Af
DETECTIoN
cIRCUIT
i30l
r
Ots
@
(oN)
JK
3
ã
ù
¡
¡
t
,H
_,1
@
(oN)
TRl
TR1I5
r----------
Muting
c¡rcuit
I
__
_J
"'I
t0
lññiilînsl
(ouiñciñnÌ"e)
lu¡r
I
(oN)
T_
I
TR3C9
__J
WIDE
li¡,¡-¡æl
indicaior
@8
To
discriminating
amplifier
tuh
CIRCUIT
(I
F
BAND
SWiTCHING.OVER)
Fig.
1
@
t¡¡toe.ruanBoW
swirching
círcuit
(During
detuning)
Negative
potentbl
is'cleveloped.at
iþe
TR437
to
turn
"ON,j
TR304,
rhe
coil
turning
"OFF"
of
TR305,
negative po
collector
of
T8415.
since
this
porent¡ar
is
impresed
to
T8304
throu
ector
is reCuced
to
ground
poteniiel,
thus
turning
TR305
,,OFF,,
Upon
tential
appears
at
ihe collector,
w¡th
vo¡tage
lower
than
"pitch-off"
being
applied
ro
the
gare
of
TR30g
to
,,OpE
N"
the
circuit
bet'¿/egn
drain
and
source.
Meanwhiie,
turnihg
"OFF"
oí
TR305
turns
"ON"
T8306
to
render
the
colfecior
of
TB306
ro
be
of
ground
porenrial,
with
d
T8307
brought
inro,,SHORT,,
srare.
L_______
MUTING
SWI
I
I
_J
\:7
ú
trequency
output
!VIDE
F
deteciion
NARROW
(narrow
range)
tF
detect¡on
300kHz
coil
af
ånpl¡íier
¿f
smpl¡fier
200kH¿
coil
@
(oFF)
F
SELECl)
S1V)
TR4I7
AF
Iherefore,
during
cletuning,
NAR
ROW
lF
raín
and
source
of