Text preview for : hfe_pioneer_tx-9500_ii_service.pdf part of Pioneer hfe pioneer tx-9500 ii service Pioneer Audio TX-9500 hfe_pioneer_tx-9500_ii_service.pdf
Back to : hfe_pioneer_tx-9500_ii_se | Home
-l';)
-
-4
fe;
.. *'!:4.-"'
f)-
{t.1i
n
\t ( A--a'
(6.' ot^'o"
-"*' "*"
IIJSlll
r-
(DrqoNEErl
TX-g'5ClCltr
MODELTX-gsOOII
COMES FOURVERSIONS
tN DISTINGUISHED FOLLOWS:
AS
Type Voltage Remarks
KC CSA (Canada) approved with de-emphasisselector switch
120V only
(25psl75psl
KU UL (U.S.A.) approved with de-emphasisselector switch
120V only
l25trs/75psl
HG S E M K O ( S w e d e n ) ,N E M K O ( N o r w a y ) , D E M K O ( D e n m a r k )
22OY and 240V (Switchabte)
and El (Finland) approved
S General export model with de-emphasisselector switch
110V, 120V,22OVand240V (Switchabte)
l25ysl50ps/75psl
. Serviceinformations TX-9500II/KUis described page through52 in this manual.
for on 5
o For servacing Kc, S and HG typesplease
of refer to TX-9500II/KU manualwith the exceptionof
descriptions the "AdditionalService
in Manual"(p.53-p.86).
CONTENTS
1. SPECIFICATIONS 5
2. CONNECTIODIAGRAM
N 6
3. F R O N TP A N E LF A C I L I T I E S 7
4. B L O C KD I A G R A M I
5. CIRCUIT ESCRIPTIONS
D
5.1 AM Tuner 11
5.2 FM Tuner 11
5 . 3 R E CL E V E LC H E C KSignal
Generator
Circuit 15
5.4 PowerSupplyCircuit 15
6. DISASSEMBLY 16
7. PARTSLOCATION
7.1 Front Panel
View 17
7.2 Front View with Panel Removed 18
7.3 Top View 19
7.4 RearPanelView 20
8. DIALCORD TRINGING
S 21
9. ADJUSTMENTS
9.1 FM Section 22
9.2 AM Section 26
10. EXPLODED IEWS
V
10.1 Top Side 27
1O.2 Bottom Side . 29
Washers Nut
10.3 Nomenclature Screws,
of and ...... 31
11. PACKING 32
12. SCHEMATIC DIAGRAMS, P.C.BOARDPATTERNS AND PARTSLIST *
12.1 Schematic Diagram and Miscellaneous List Parts 33
12.2 FM Front End (AWB-023). 36
1 2 . 3 A M F M l F A s s e m b l( A W E - 0 7 0.). .
y 37
12.4 MPX AF Assembly (AWD-009) 45
12.5 PowerSupplyAssembly (AWR'128) 50
Manual
AdditionalService
1. CONTRAST F MISCELLANEOUS RTS
O PA 54
2. KC TYPE
Diagram
2.1 Schematic and Miscellaneous List
Parts 56
2.2 PowerSupplyAssembly(AWR-I29) 59
2.3 Packing 61
3. HGTYPE
Diagram
3.1 Schematic and Miscellaneous List
Parts 62
3.2 MPX AF Assembly(AWD-008) 65
3.3 PowerSupplyAssembly(AWR'I30) 70
3.4 Packing 73
4. S TYPE
Diagram
4.1 Schematic and Miscellaneous List
Parts 74
4.2 MPX AF Assembly(AWD-010) 77
4.3 PowerSupplyAssembly(AWR-I31) .. . . 82
(AWX-113). .
4.4 SwitchAssembly 85
4.5 Packing 86
TX-s|5clCltr
1. SPEC|FtCATIONS
Semiconductors AM Section
FETS 5 Circuitry ...lstageRFamplifier3-gang
lCs 15 variablecapacitor
Transistors ......12 Sensitivity
Diodes ....19 l H F , f e r r i t e a n t e n n a. .
. 300pV
l H F , e x t e r n aa n t e n n a. .
l 15pV
FM Section Selectivity . . 30dB
Circuitry . . . MOS FET 2-stageRF ampli- S i g n a l - t o - N o i Re t i o . . . . .
sa 55dB
fier, 5-gang variable capacitor, 70dB
l m a g eR e s p o n sR a t i o . . . .
e
l F B a n d S e l e c t o rW i d e - b a n d
,
l F R e s o o n s e R a t.i .o . . . . 65dB
linear detector, doublebal- Antenna ... Built-in ferrite loopstick
anced NFB type PLL MPX antenna
b u i l t - i n pi l o t s i g n a l a u t o
canceer. ll Audio Section
Usable ensitivity .
S . MONO: 8 . 8 d B f( 1 . 5 9 V ) Output ( Level/l pedance)
m
/r 5 0 d BQ u i e t i n g e n s i t i v i t . . M O N O :
S y 1 3 . 2 d B f( 2 . 5 t N ) FM ('100% OD.)
M FIXED: 650mV/4.2kO
l STEREO: 36.1dBf 35pV) ( V A R I A B L E : 5 0 m Vt o
S i g n a l - t o - N o i Re t i o
sa 1.3V/3.6ks2
at 65dBf MONO: 82dB A M ( 3 0 %M O D . ) . FIXED: 2OOnYl4.2kQ
'l5mV
STEREO:71dB VARIABLE: to
wlDE NARRow 400mV/3.6kO
Distortion t 65dBf
a MoNo:
Miscellaneous
100H2 0.05% O.OIY,
l kHz 0.05% O.jlY' P o w e rR e q u i r e m e n t s 1 2 0 V 6 0 H zo n l y .
10kHz O.07o/o 0.1Yo PowerConsumption . . . . 25W .
15kHz 0.12Y" Dimensions . a 2 0 ( W ) x 1 5 0 ( H ) x 3 9 5 ( D )r r
m
STEREO: 1 6-9 1 6x5-718x1
| 5-9l16 in
100H2 0.17o O.3Vo Weight .... WithoutPackage:
l kHz 0.07o/o 0.25% 9 . 5 k g( 2 0 1 b 5 o z )
1
lOkHz 0.2Yo 0.5%o With Package:
15kHz O.57o 1 1.0kg (241b oz) 4
Capture atio..
R . 0.8d8 2.0d8 Parts
Furnished
A l t e r n a t e h a n n eS e l e c t i v i t y .
C l . . 35dB 85dB ....1
FMT-typeantenna
StereoSeparation.. ..lkHz: 50dB 45dB ......1
Operatinglnstructions
5 0 H z t o 15 k H z : 3 5 d B 30dB .....I
ConnectionCordwithPinPlugs
Frequency esponse R 2 0 H zt o 1 0 k H z + 0 . 2 d B H e x .W r e n c h u s e d o r f a s t e n i n g T u n i n k n o b ) . . . . . . . 1
( f g
2oHz r stHzloo']aa
to
S p u r i o u s e s p o n sR a t i o . .
R e 11OdB NOTE:
l m a g eR e s p o n sR a t i o . . . .
e 120d8 Specificationsand.the designsubject to possiblemodifica-
l F R e s p o n sR a t i o .
e 105dB tion without notice.
A M S u p p r e s s i o na t i o . . . .
R 65dB
M u t i n gT h r e s h o l d .. 1 9 . 2 d B f ( 5t Y ) , 3 4 . 1 d 8 f ( 2 8 p v )
t
S u b c a r r i eP r o d u c tR a t i o . .
r 11dB
SCA ReiectionRatio . . . . . 62dB
A n t e n n a l n p u.t ... 30Oohmsbalanced
75ohms nbalanced
u
DIAGRAM
2. CONNECTION
>t
T TYPE
FM DE.EMPHASIS SWITCH AM ANTENNA FM ANTENNA FM OUTDOOR
Normafly, set this s,witch to "75tts." (indoor or outdoorl (if stations nearby) ANTENNA
are
Be sure to set it to "25ps." only when D I S C R E T E4 C H A N N E L
I *-J-=
FM ADAPTOR
listening to an FM broadcast (pre-
emphasis: 25psl with a Dolby* system.
rl !
i----
I I
{t
TX-9500[
AM FERRITEBAR ANTENNA
C O N V:E ] l\ E N r
N
-)
OUTLET ( n o t
iT
coupled i t h
Iwv I
power w i t
power sr'\,c h )
"l
lf-
lls t-
tl tl
| lr
I
L-
t=J
lr5
_JTII
GROUND
oosoo16;sO
b'ossoifdon
O S C IL L O S C O P E T A P ED E C K S T E R E OA M P L I F I E R
* T h e w o r d " D o l b y " i s a t r a d e m a r ko f D o l b v L a b o r a t o r i e s n c .
I
3. FRONT PANEL FACILITIES
POWERSWITCH S I G N A LM E T E R TUNING
Set to ON positionto turn on power.Pilot lamp will light. Employ when tuning AM and FM stations. ptimum O Use whe
tuning p o i n t o c c u r s w h e n maximum meter deflection deflectio
toward the right is obtained. tune care
(optimum
t F B A N DI N D I C A T O R
P I L O TL A M P
IF BAND SWITCH
F M l F ( i n t e r m e d i a tfrequency)passband
e can be set to
for wide or narrow.
WIDE: Normallysetswitchto this position.
NARROW: lf adjacentstation interference a pro-
is
blem at the WIDE setting,set switch to
t h i sp o s i t i o n .
M U L T T P A T H / R EL E V E L C H E C KS W T T C H
C MEMORY ARKERS
M
Singleleveroperates both MULTIPATH and REC LEVEL Convenientfor designating most often tuned in stations.
CHECK switches. With the FUNCTION switchat FM, set Slidemarkerswith fingertipto desiredpositions.
as requiredfor the application. Be sureto return it to the
MUTING
OFF positionwhen it is not beingused.
MULTIPATH ON: Multipath sound becomesaudible Controls
from speakers. When installing FM noisewh
antenna, select antenna location and op
tuning
direction so as to minimize this sound. 2:
OFF: Normallyset switchto this position.
O U T P U TL E V E L C O N T R O L
REC LEVEL CHECK ON: Use this position for setting
Adjustslevel OUTPUT
at jacks.
(VARIABLE) Clockwise
recording levels of tape deck. A 44OHz
rotationincreases
output level. OFF:
signal (level corresponding 50% FM
to
modulation) is produced at approxi-
mately 1.7 second intervals.
TX-s|5ClCltr
T U N I N GM E T E R F M S T E R E OI N D I C A T O R
;. Optimum Use when tuning FM stationsFirst tune for maximum
. with the FUNCTTON witch set to FM AUTO (or FM
s
' deflection
d e f l e c t i o n f t h e S I G N A L m e t e r ( t o v , a r d h e r i g h t ) ,t h e n
o t N O I S E F I L T E R ) , t h e i n d i c a r o rw i l l l i g h t d u r i n gs t e r e o
tune carefully so that the meter indicates centerof scale signalreception.
( o p t i m u mt u n i n gp o i n t ) .
)ICATOR
FUNCTION WITCH
S
Switch for selecting type of reception.
AM: AM broadcast reception.
FM AUTO: FM stereoreception.lf broadcast FM is
mono, the mono mode is automatically
selected.
F M N O I S E F I L T E R : S e r t o t h i s p o s i t i o ni f c o m p a r a -
tively high frequency noise becomes
objectionable during FM stereoreception.
Note that some lossof stereoseparation
)' occursat this position.
FM MONO: FM monophonic reception.Set to this
-_l oraorueen srEFEo
ruNEril-9500]l position if receptionat FM AUTO posi-
tion is noisyor signals weak.
I M U T I N GS W I T C H
Controls circuit for cancellingbothersomeinterstation
___l
noise when tuning FM stationsto providea comfortable T U N I N GK N O B
tuning operation.
Knob for selecting stations.Refer to the SIGNAL meter
2: Set to this position to receiveonly strong
when tuning AM stations and to both SIGNAL and
stations.
T U N I N G m e t e r s h e nt u n i n gF M s t a t i o n s .
w
1: lf desiredstationcannotbe received position
at
Clockwise 2, set switchto this position.
OFF: Set to this position in locationswhere signals
areextremelyweak.
a
4. BLOCK DIAGRAM
F I , {F R O N T N D
E
-- - SWITCHES.
l'--
!. crq
Rr -;
rctr*@l
R Fa m ;
-5.@l
f l1 x* "r
ii e
I S'a^t ' FUNCTI0
1 .A M 7 . F
r4 I lr'i I lrefl+
,F
15o S z , r , b: M U T I N G
FX 1 OFF 7.
I t S:a'd ' f40DE
L
It--- --i--L-- --_ --/ t L--r
3000 1. IIULTiP
L
S4a,b' lF BAND
CND NARROW <-
(. v J POW ER
1 Buffen
Loca 0SC
| 0N <--) OFF
55 D E -E N P H
F 1 1 F A H P L I F I E R& D E T E C T O R
I
t- WIDE
F Md e t e c t o n
n*ftr;--rtr;-\
L = J r = L L 4 L d
Frf ---1r Yr r7
--t --1 --1
NARROW
T
W I D Er n d .
Ceramic C e r ^ aim
c
L filfen filfer^
NARROW d
ln
J
e
J 1 A
F I 1I F A M P I C
TUNING
meter'
M U T I N GC O N T R
CIRCUIT
SIGNAL mefer-
Al1Our
__J
A I 1 T UN E R
SWITCHES.
S'a^ t : FU CTION
N
1 .A M 2 F I ' 1 U T O 3 , F I " ]I 1 P X N O I S EF I L T E R 4 . F M I 4 O N O
A
S 2 , r ,b i I l U T IN G
1 OFF ?. 1 3.2
S34- d : 11OE D
1 . I I U L T I P A T H N 2 . O F F 3 . R E CL E V E IC H E C K N
O O
S4a,b ' lF BAND
NARROW E WIDE
S e p aa t i o n a d L
r
(. ' POWER
0N --+ 0FF
56 : D E -E N P l t n S f
S 25aS *-t5l.5
- I F I E R - &D E T E - T O R
C T1PXDEMODULATOR OUTPUT
F M e te cl -on
d L E V E L OUTPUT
*+ - ; " r t I
1--th-Xl I r'rct' : 3 lr
VARIABTE
,
L.PF.
S t,q
6
\i A F M U T .I C
RJ
o Stn
3
L REC VEL C.
LE OS
-_Jl l--r--.l o
5os
L-r
rLs.-^ --i
I o q.
FIXED
Rr
I "JU
l*r
L------r'\ |
src I IS'a U:- --J
A F M U T I N GC I R C U I T
r ULTIPATH
HORIZ
(DtT OUT)
VERT
Q+va
.J5
#c-->AC LINE
l__ __ L
_)
POWER UPPLY
S
TX-s|E'clcltr
5. CIRCUIT DESCRIPTIONS
5.1 AM TUNER 5.2 FM TUNER
The major components of the AM tuner are the FM Front-end
3-ganged variable capacitor, a newly developed IC The FM front end is composed of a tuning circuit
(HA1197), and an AM ceramic filter. A block employing a 5-gangvariable capacitor, a 2-stage RF
diagram of the HAlL97 is shown in Fig. 1. amplifier a mixer employing dual gate MOS FETs,
This IC consists of an RF amplifier first stage, and a local oscillator with buffer. An equiva-
followed by a mixer stage which also includes a lent of a cascode amplifier is produced by AC
self-oscillating local oscillator, the IF amplifier 3rd grounding gate-2 of the dual gate MOS FET,
and 4th stages, and a detector circuit final stage. allowing stable RF amplification at high gain.
The AGC (Automatic Gain Control) receives an The output signal of the RF amplifier is applied to
AGC voltage from the output of the detector cir- gate-l of the mixer stageMOS FET, while the local
cuit, and applies it to the RF amplifier and IF oscillator output signal is applied to gate-2. This
amplifier stages.The advantageof the HA1197 is a technique minimizes input power from the local
large reduction in the distortion at low frequencies. oscillator, resulting in low mutual interference even
Whereas the distortion at 100H2 was 1.57oin the if the received signal input level is high.
previous HA1138, this figure has been reduced to A variation of a Clapp circuit forms the local
0.4Vo (LOOHz) the HA1197.
in oscillator. Inclusion of a buffer amplifier between
local oscillator and mixer reduces local oscillator
load, eliminating distortion of the oscillation wave-
form. Drawing effect of the local oscillator is also
eliminated.
C e r a m i cf i l t e r
ANT
AF out
AGC line
To SIGNAL Meter
F i g . 1 B l o c kd i a g r a m f H A l 1 9 7
o
1 s tR F a m p . 2nd RF amp
FM 75O UNBAL.
t-
FM 3OOOBAL.
L
Local oscillator
F i g .2 C i r c u i to f F M f r o n t e n d
FM lF Amplifier a conducting state, with the signal passinginto the
In this FM IF amplifier, there are two selectable IF next stage.
frequency pass bands,viz. WIDE band and NAR- Following the IF amplifier in NARROW band, or
ROW band, selectedby the IF BAND switch. following the WIDE band circuit there is a 5-stage
This circuit is shown in Fig. 3. wide-band IF amplifier which produces sufficient
The SAW (Surface Acoustic Wave) filter used in limiter effect.
the WIDE band circuit, is a filter which works on FM Detector
entirely new principles. Signals are carried across The detector circuit used in the TX-9500II is a
the piezoelectric element surface by mechanical super wide band linear detector circuit, a product
vibrations. The advantages of this SAW filter in resulting from the study of distributed constant
comparison with a 2-element ceramic filter, is that type detectors.
the group delay time flatness characteristics cover The circuit is shown in Fig. 4.
more than twice (500H2) the band width while M5109PR included in this circuit is an IC incor-
still maintaining the same degree of selectivity. porating 2 pairs of differential amplifiers. The
The tetra-polar phase linear filter makes use of the
loads of each differential amplifier are connected
SAW filter characteristics to further improve the to a series resonance circuit where the L16, C3t
degree of selectivity. Consequently, the WIDE resonance frequency is higher than the inter-
band circuit has been designed with the aim of mediate frequency (10.7MH2), and the L,r, C.,
even further improving the distortion factor. resonance frequency is lower. The IF outputs
The NARROW band circuit employs 5 2-element from each of these differential amplifiers are
ceramic filters for very good selectivity. This cir- modulated to the AM components which are then
cuit is outstanding in its ability to reject interfering detectedby Dr - D6.
signals, and is particularly suitable for areas where
adjacent stations are crowded very close together
on the FM band. The distortion factor too, is very
close to the value obtained in the WIDE band.
lF omp e l
Switching between the WIDE and NARROW bands
is accomplished by switching a +B voltage supply
stoge ir
r r o! l <--H/v\# ComPoSlre
ON and OFF. But since the IF amplifier in the I I signol
r qi l
NARROW band circuit is the same IF amplifier ,t4 IT
t' I
used to operate the meters and the muting func- L---- --J
tion, the +B voltage supply for the final stage IC M5I09PR
and diode (Dt) would also be turned ON and OFF.
Switching the +B voltage supply for Dt ON and Fig. 4 Circuit of FM detector
OFF will cause D1 to act as a switch. When the +B
voltage is applied to the anode of D1, Dr is put into
fz
-JH|--1-IF--r
B -+-
\ - d - q - d
.\ -\
+ 'r -1-
I ?d T-{ f-{
'" 1-
'rz ,7
,z
Phose fi tter
W I D Eb q n d I F AMP.
L_____ _.t\_a&toy d l F A M P
bon
F I V M U T l N GC ] R C U I T
F i g .3 C i r c u i to f F M l F a m p l i f i e r
TX-s'E'clOtr
Anti-birdy Filter outstanding dynamic range, S/N ratio, and distor-
The function of this filter is to remove any com- tion factor. De-emphasisis provided by inserting
ponent signals belonging to adjacent stations a time constant circuit in the NFB loop of the AF
within 200kHz of the tuned station which are amplifier. The elements in this time constant
still contained in the signal after detection. If it circuit include a metal film resistor (lVo tolerance)
were not for this filter, beating in resonance with and a polystyrene film capacitor (27o tolerance)
the 10th and 11th harmonics of the 19kHz pilot which have made it possibleto reduce de-emphasis
signal generated in the MPX IC of the final stage deviation to within +0.2d8 to -0.5dB in the 20Hz
would occur, and appear as noise in the reproduced to 15kHz range.
signal. The switching circuit for the muting function is
activated when a DC voltage from the power
FM Multiplex Decoder ON/OFF detector section or from terminal no.8,
This section includes another IC recently devel- is received. The signal circuit is then connected to
oped by Pioneer, the PA1001. See Fig. 5 for the gtound, thus preventing the output of any signals.
block diagram. This power ON/OFF detector circuit detects the
This IC, an improvement over a previous IC instantaneous change when the POWER switch
(HA1196), incorporates a pilot auto-canceller is turned ON or OFF, sending a trigger signal to
circuit. This circuit filters out the leak canier the switching circuit, and thus activating the
(19kHz) contained in the demodulated signal muting function. As a result, the popping noise
without any loss in the frequency characteristics usually generated when the POWER switch is
of the audio signal. This filtering action is a con- turned ON or OFF, plus the residual noise, is
siderable improvement over the previous low pass eliminated.
filter method. Other features include a wider
input dynamic range, and the ability to perform
well even when a 3O0Vo modulated input signal is
applied to the IC. S/N ratio and distortion factor
have also been improved by the incorporation
of a NFB circuit in the decoder amplifier. Distor-
tion has also been improved in the case of MONO
signals by connecting together the output circuits
of the L and R channels, and thus cancelling the
out-of-phase distortion components contained in
the L and R channel audio signals.
r -_l
+l
our
R
F i g .6 B l o c kd i a g r a m f P A 1 0 0 2
o
FM Control Circuit
The FM control circuit used to control the meter
drive and FM muting circuits, is independent of the
TO STEREOnd
i audio signal circuitry. This circuit, too, incorpo-
rates an IC (PA3001) recently developed by
Pioneer. The block diagram is shown in Fig. 8.
Fig.5 Block
diagram PA1001
of
The PA3001 is very similar to the previous IC
(HA1137) in function and operation. It differs in
AF Amplifier and Muting that the FM muting level can be controlled extemal
This circuit employs the Pioneer developed IC to the IC. The input signal is supplied by the IF
(PA1002). The block diagramis shown in Fig. 6. amplifier in NARROW band (See Fig. 7).
This AF amplifier is a direct coupled amplifier The FM muting function in the TX-9500II works
used as a differential NFB amplifier providing in 5 different ways:
13
1. Muting of the noise contained in the received two. The adjustments are made by the semi-
signal. variable resistors VR+ and VRr respectively. The
2. Muting at a specific antenna input level. output of terminal no.1-2 of PA3001.is connected
3. Muting when not tuned to any station. via 32-6 and 53 to terminal no.8 of PA1002, so
4. Muting when the IF BAND switch is switched. that when an output voltage in excess of 1.3V
5. Muting when the FUNCTION switch is switched. appeani at terminal no.12 of PA3001, the switch
The disconnection of the signal circuitry during circuit in PA1002 is activated, thus bringing the
all of the above mentioned muting actions, is muting circuit into operation.
performed by means of a switch circuit incor- 3. Muting when not tuned to any station
porated inside the PA1002 IC. When the tuned frequencies separated by about
1. Muting of the noise contained in the received x70kHz from the broadcasting frequency, a DC
signal voltage appears at terminal no.L2 of PA3001. This
Detection of this noise component is performed voltage activates the switch circuit incorporated
in the NOISE amplifier (Qtt, high passfilter, Q'e) inside PA1001, thus bring the muting circuit into
shown in Fig. 7. After detection, the audio signal operation.
appearsat terminal no.6 of PA3001, with the noise 4. Muting when the IF BAND switch is switched
components above 100kHz contained within this The Qrq basevoltage is designedto drop to 0V dur-
audio signal being detected and amplified by the ing the instant the IF BAND switch (Sa) is changed.
NOISE amplifier. The output of this NOISE am- (both contacts open during the switching action).
plifier (noise component) is rectified at D13 and Consequently, Qtn is turned ON, resulting in +B
D1a, and then removed as a DC voltage. passingvia Q1e to charge Crr, as well as passingvia
This DC voltage is passed via Sr-b (MUTING Dp to terminal no.8 of PA1002, whose switch cir-
switch) and Sr (MODE switch), finally being ap- cuit is then activated.
plied to terminal no.8 of PA1002. When the audio 5. Muting when the FUNCTION switch is switched
signal contains a high level of high frequency noise, The Qrq base voltage drops to 0V during the in-
the PA1002 switch circuit is activated, resulting stant when the FUNCTION switch (Sr) is tumed
in the signal circuit being shorted to ground. from AM to FM, resulting in the momentar5r
2. Muting at a specifrc antenna input level opening of the +B switching section of the FUNC-
The DC voltage at terminal no.L2 of PA3001 is TION switch. This results in Q,, tuming ON, with
set to read at least 1.3V when the antenna input is all consequent steps being the same as when the IF
less than 14dB (5pV) with the MUTING switch in BAND switch was changed.
position 1, and less than 29dB (28pY) in position Furthermore, Q2 has been added to the circuit in
WIDEIF IF AMP. MPX IC A F M U TI C L OUT
t^ (PAl002)
( PA100)
t
DETECTOR I R OUT
FM FUNCTION
+Br
+B
+Be'
+d3
F?
h po.ss iLter
f
sr_b
?t'
v>
Sz : MUTING FF-I- 2
O
Sr : MODE
TUNING eter
m
I V U L T I P A T H - O F F - R E E V E L C H E C KO N
LC
SIGNAL eter
m Sa: lF BAND
MULTIPATH WIDE NARROW
F i g .7 F M c o n t r o lc i r c u i t
TX-s|5clcltr
order to prevent muting when the FUNCTION (HA1452W), produces tone bursts every 8.4 sec.
switch is tumed to the AIVI position. In this case for 1.7 sec. intervals by means of. a 440H2 signal.
+Bz is applied to the bases of both Q1e and ez, The output level corresponds to a value equivalent
turning Qre OFF, and Qz ON. Therefore, terminal to an FM broadcast with 5O7o modulation. The cir-
no.8 of PA1002 is connected to ground, thus pre- cuit is outlined in Fig. 9.
venting the muting circuit from operating. The IC HA1452W incorporates two pairs of opera-
The muting action is also inhibited when the tional amplifiers, one being used as a 440H2 sine
MODE switch (S3) is tumed to the REC LEVEL wave oscillator circuit, and the other as square
CHECK position. In this case, the MODE switch wave oscillator, which cycles on and off every 3.4
shorts terminal no.8 directly to ground. sec. for 1.7 sec. The switching action of e, con-
verts this square wave into tone bursts. When the
square wave is applied to the ba