Realistic STA-85 User manual

ruLrstC.
Seruice
STA.85
AM /FM STEREO RECEIVER
Catalog Number:31 -2061
" cusloM MANUFACIURED FoB RADIo sHACK[|R orvrstoN 0F rANDy conponAloN

CONTENTS
SPECIFICATIONS 3 & 4
BLOCK D|AGRAM.......... ......................... 5
D|SASSEMBLY TNSTRUCTTONS ......... ................... 6
DIAL STRINGING DIAGRAM .............. 6
ALIGNMENTPROCEDURE 7_9
LEVEL DTAGRAM .......... ...................... 10
ALIGNMENT & CHECK POINTS .......... 11
TROUBLESHOOTTNG ............. .... 12 _ 16
0055 TUNER 8OARD................ . 17 & 18
6053 AUDTO AMp BOARD ........ 19 & 20
SEMICONDUCTOR LEAD IDENTIFICATIONS................. 21
ELECTRICAL PARTS LIST
MISCELLANEOUS PARTS LIST
SCHEMATIC DIAGRAM SEPARATE SHEET
EXPLODED VIEW SEPARATE SHEET
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
22-29
30
,l

SPECIFICATIONS
NOMINAL LIMIT UNIT
FM SECTION
1. TUNING COVERAGE
2. DIAL CALIBRATION ACCURACY 90 MHz
98 MHz
3. usABLE sENsrrvrrY 106 MHz
(NOTSE & DTSTORTTON -30 dB)
4. IMAGE REJECTION (at 98 MHz)
5. lF REJECTION (at g0 MHz)
6. FULL LIMITING (at -3 dB)
7. lF BANDWIDTH (6 dB down)
8. DISTORTION (1 mV INPUT)
9. SIGNAL-TO-NOISE RATIO (1 mV INPUT)
10. DE-EMPHASIS 75 trrsec. (at 50-10000 Hz)
11. DISCRIMINATOR BANDWIDTH (Peak-to-Peak)
12. AFC HOLDING RANGE (with 1 mV signal)
13. OUTPUT VOLTAGE MONO
(at 75 kHz dev.,400 Hz mod., 1 mV input) STEREO
14, MUTING THRESHOLD
15. OVERLOAD THD (at 98 MHz, 100% mod.)
100 mV RF INPUT
16. SPURIOUS RESPONSE at 98 MHz
ANTENNA INPUT 3pV,1l2 1F,103.35 MHz
17. CAPTURE RATIO (1 mV INPUT)
18. ALTERNATE CHANNEL SELECTIVITY
(100 pV INPUT)
M PX SECTION
1. STEREO SEPARATION 100 Hz
(100% mod., 1 mV input) 1 kHz
10 kHz
2, DISTORTION
(100% mod. 1 mV input) 1 kl.{z
3. STEREO BEACON SENSITIVITY (pilot 7%)
4. RESIDUAL 19 kHz & 38 kHz (1 mV input)
5. SUPPRESSION OF SCA INTERFERENCE
(1 mV input)
AM SECTION
1. TUNING COVERAGE
2, DIAL CALIBRATION ACCURACY 600 KHZ
1,000 kHz
1,400 kHz
3. USABLE SENSITIVITY 600 kH2,1000 kHz, 1400 kHz
(400 H2,30% mod., Radiated
noise & distortion -20 dB) Direct
4. IMAGE REJECTION (at 1,400 kHz)
5. lF REJECTION (at 600 kHz)
6. AGC FIGURE OF MERIT
(from 100 mV/m at 1,000 kHz)
7, DISTORTION
(400 Hz, 30% mod., 5 mV/m input)
L IF BANDWIDTH (6 dB down)
9. OUTPUT VOLTAGE
(1 kHz 30% mod., 5 mV/m input)
87.5-108.5
0.3
65
r1.5
400
r1000
750
650
5
1
80
2.0
6
50
80
2.O
2
50
38
40
30
0.5
10
50
250
25
35
30
45
1.5
510-1660
250
88-108
t250
1350
r250
3.0
10
45
70
3.0
t1 50
0.8
58
!2
300
1800
75012 dB
650t2 dB
4-16
1.5
70
3.5
40
27
32
20
1.2
3-16
40
40
520-1620
r15
t30
t40
2.5
6-14
200
500
40
30
25
30
MHz
kHz
kHz
kHz
prV
dBf
dB
dB
pV
kHz
o/
/o
dB
dB
kHz
kHz
mV
mV
pV
o/
/o
dB
dB
dB
dB
o/
/o
dB
dB
kHz
kHz
kHz
kHz
pV lm
pV
dB
dB
dB
o/
/o
kHz
mV
pV
dB
dB

NOMINAL LIMIT UNIT
11.
12.
10. AUDIO RESPONSE
(5 mV/m input from 400 Hz to 3 kHz, 0 dB @1,000 kHz)
SELECTIVITY 200 pYlm
SIGNAL.TO-NOISE RATIO
(1000 kHz, with antenna input 5 mV/m)
AM BEAT (input 5 mV/m)
AUDIO SECTION
1. RMS OUTPUT POWER
(distortion (:0.3o/o,20 Hz - 20 kHz)
PER CHANNEL DRIVEN 8 O
BOTH CHANNELS DRIVEN 3 3
(lHF power @ 1 kHz,8 Sl, t1 dB)4 O
2. IM DISTORTION
(at 25 W output TO|T,OOAHz 411l
3. HARMONIC DISTORTION lat 25 W output)
100 Hz
1,000 Hz
10,000 Hz
4. FREOUENCY RESPONSE
(AUX, 8 Sl load, 1 W output, 30 Hz - 20 kHz)
5. INPUT SENSITIVITY (for 35 W output) PHONO
AUX
TAPE MON
PHONO
AUX
TAPE MON
BASS 100 Hz
TREBLE 10 kHz
8. EOUALIZATION RIAA: 30- 15,000 Hz
9. PHONO AMP OVER LOAD CAPABILITY (at 1%)
10. HIGH FILTER
11. LOUDNESS COMPENSATION (volume -30 dB)
12. CHANNEL SEPARATION
(AUX input 100 - 10,000 Hz)
13. SIcNAL-TO-NOISE RATTO (input shorted)
PHONO
AUX
14. RESIDUAL NOISE
15. LOAD IMPEDANCE
16. POWER SOURCE
20 WATTS, No Signal
170 WATTS, Full Signal
120 Volts,60 Hz AC*
13.
6. INPUT IMPEDANCE
7. TONE CONTROL
10 kHz
10 kHz
100 Hz
-4
28
40
50
55
40
45
0.2
0.1
0.1
o.2
r1
2.8
180
180
50K
70K
70K
r10
tg
120
-64
10
40
60
70
1.5
-6
20
32
10
40
45
35
35
0.5
0.15
0.15
0.3
r1.5
2.810.5
1 80r40
1 80r40
!10!2
!8!2
RIAAt2
100
-6!2
4!2
10t2
35
55
60
3
4-16
dB
dB
dB
o/
/o
W
W
W
W
o/
/o
o/
lo
o/
lo
o/
/o
dB
mV
mV
mV
ohm
ohm
ohm
dB
dB
dB
mV
dB
dB
dB
dB
dB
dB
mV
ohm
* 2201240 VAC, 50 Hz for European and Australian Models.
NOTE: Nominal Specs represent the design specs; all units should be able to approximate these-some
will exceed and some may drop slightly below these specs. Limit Specs represent the absolute
worst condition which still might be considered acceptable; in no case should a unit perform
to less than within any Limit Spec.
4

BLOCK DIAGRAM ;
o\
= E PH
i E-.dr =
E9 t-Jt A
E E:; *'E E
ee
H:=
==3
_l
E
al--=*= =:
ll
5
I
;
I+t't
=
t.F t't
=
33; =
==
z
=
LA- E--, -: :--.,]
:
=
<=e ==I
=r t
Er
-3
t
=:
=F
-= E3-
t==
AF
=F tEl
==
Es
at =
t- _-
==
ts= o I =,s
9l
t6
^_]
,*l
l
l
_l
I<F
zq;
6
t-
o=3
3! ,9
=
=---r-
I
I
I
___l_ 1
i; =
.l
i
l-r
t
=
=q
o-
Eo
---r
II
E
E
II
r
=
t=l
!l___l
_J&*
I
=
l
=<=
==
9=
Z6 ==
=a
E
2
==l
:l
-l =
=
=
V-)
E=
!==
=
E=E
7
l.
=9 )*l T
=
o
e
=
;=s =3
=9
=
cE
=-
E
E
=F
I
=
=oF
;> o
o
= : E= E:=:
g = E=E::=

DISASSEM BLY INSTRUCTIONS
1. Removing chassis from wooden cabinet. (Refer to Fig. A)
Remove the five screws (#58 & #66) from both sides of the wooden cabinet and back panel.
2. Removing the Front Panel. (Hefer to Fig. A)
a) Remove the knobs from SELECTOR, SPEAKERS, BASS, TREBLE, Tuning and VOLUME.
b) Remove six screws (#65) from both side of Front Panel and remove panel.
@
^(
rC
a, ^lA)
\D*
Fig. A@(B
DIAL STRINGING DIAGRAM
Note: Tuning capacitor should be in fully closed position.
{d
@-/:\
^_e
ar^
rurrnc srarr zf

ALIGNMENT PROCEDURES
Do not attempt alignment unless the following equipment is available.
Note: Remove line cord antenna from FM external antenna terminal
1. AM Signal Generator
2. Oscilloscope
3. AC Voltmeter
4. FM Signal Generator
5. Stereo Modulator
6. Audio Generator
7. Distortion meter
8. DC Voltmeter
9. Frequency Counter
when aligning.
AM IF & RF ALIGNMENT
RECEIVER
Loop Antenna
L451
Fis. 1 AM ALIGNMENT CONNECTION
TAPE OUT --l
Output of signal generator should be no higher than necessary to obtain an output reading.
Signal Generator Modulation: 30%
Set SELECTOR switch SWl to AM.
STEP SIGNAL
GENERATOR
COUPLING
SIGNAL
GENERATOR
FREOUENCY
R ECEIVER
DIAL
SETTING INDICATOR ADJUSTMENT
Refer Fig. 4. REMARKS
1Refer Fig. 1455 kHz
(400 Hz Mod.)
Point of non-
i nterference
(on/about
600 kHz)
AC Voltmeter
to TAPE OUT
jack T402 flFT) Adjust for maxi-
mum reading.
2Same as Step 1600 kHz
(400 Hz Mod.) 600 kHz Same as Step 1L402 (OSC Coil)
1451 (ANT Coil) Same as Step 1
3Same as Step 11400 kHz
(400 Hz Mod.) 1400 kHz Same as Step 1
TC1 05
(OSC Trimmer)
TC1 04
(ANT Trimmer)
Same as Step 1
4Same as Step 11000 kHz
(400 Hz Mod.) 1 000 kHz Same as Step 1vR402 Adjust for 160
mV Audio
output.
5Same as Step 11000 kHz
(400 Hz Mod.) 1000 kHz Receiver's
SIGNAL
Meter VR4O1 Adjust lor 70o/o
reading of full
scale with input
of 5 mV/m.
Note: Remove line cord antenna from FM external antenna terminal when aligning.
'7

FM RF AND IF ALIGNMENT
Zin = 50 o (75 o)
FM Dummy Antenna to 300 S) antenna terminal of Receiver
Zout = 3OO Sl (balanced)
8
Signal generator output should be no higher than necessary to obtain an output reading.
set selector switch to FM.
Signal Generator deviation: 75k{z NOTE: Be sure to disconnect FM line cord antenna during alignment.
STEP SIGNAL
GENERATOR
COUPLING
SIGNAL
GENERATOR
FREOUENCY
RECEIVER
DIAL
SETTING INDICATOR ADJUSTMENT
Refer Fig. 4. REMARKS
1
Connect to FM
Antenna Termi-
nal through
FM Dummy
Antenna
(300 O) Fig. 2
90 MHz
(400 Hz Mod.) 90 MHz
AC Voltmeter
connected to
TAPE OUT
jack
L101
(ANT. COIL)
L102
(RF COIL)
L 103
(OSC. COIL)
Adjust for maxi-
mum reading on
AC Voltmeter.
2Same as Step 1106 MHz
(400 Hz Mod.) 106 MHz Same as Step 1
TC1 O1
(ANT. Trimmer)
TC1O2 ,
(RF Trimmer)
TC1 03
(OSC. Trimmer)
Same as Step 1
Repeat steps 1 & 2 until no further improvement is possible.
3Same as Step 190 MHz
(400 Hz Mod.) 90 MHz Same as Step 1T101 flFT) Same as Step 1
4Same as Step 198 MHz
(400 Hz Mod.) 98 MHz DC Voltmeter
connect
across R21 1
(s.9 Ks,)
T201
(Bottom Core)
Adjust for zero
reading on DC
Voltmeter.
5Same as Step 198 MHz
(400 Hz Mod.) 98 MHz
Distortion
Meter con-
nected to
TAPE OUT
jack
T201
(Top Core) Adjust for mini-
mum distortion.
6Same as Step 198 MHz
(400 Hz Mod.) 98 MHz Receiver's
SIGNAL
Meter VR2O3 Adjust for 70o/o
reading of full
scale with input
of 1 mV.
7Same as Step 198 MHz
(400 Hz Mod.) 98 MHz
Oscilloscope
connect to
TAPE OUT
jack VR2O4
Adjust so output
just appears with
an input signal
level of 5 pV.
For European model, the lowest frequency of FM tuning range should not be below 87.5 MHz.
125 sl (112.5 s))
50 a (75 a)
150 r, Fis.2 FM DUMMY ANTENNA

MPX ALIGNMENT
TAPE OUT
FM ANTENNA
TE RM I NAL RECEIVER
(300 s,) tr-
Fig.3 MPX ALIGNMENT CONNECTION
MAIN AMPLIFIER ALIGNMENT
FRONT END
L103, L101
L102, TC101
TCl02, TC103
FM SIGNAL
GENERATOR FM DUMMY
ANTENNA
300 f2
FM IF
T201
VR2O3
vR2o,4
STEREO
MODULATOR
Set SELECTOR Switch to FM.
Tune for 98 MHz on band.
Signal Generator output level: 1000pV. Deviation: 75kHz, at 100% modulation of composite signal.
Connect Signal Generator to FM Antenna Terminal through FM Dummy Antenna (300 S.)).
ST EP
19 kHz
(PILOT SIGNAL)
MODULATION
Level
SIGNAL
GENERATOR
Freq. Set to
OUTPUT
INDICATOR
Connected to ADJUST
Refer Fig. 4ADJUST
FOR NOTE
18To Composite 1 kHz
R channel
AC Voltmeter to
TAPE OUT jack
of R channel
Adjust input for
audio output of
about 0.65 V
28% Composite
1 kHz L channel
AC Voltmeter to
TAPE OUT jack
of R channel VR301 Minimum
AC Voltmeter
reading shou ld
be at least 30
dB below reading
in step 1.
38Yo Composite
1 kHz R channel
AC Voltmeter to
TAPE OUT jack
of L channel VR301 Minimum Same as Step 2.
4PILOT OFF Carrier only
Frequency
Counter Connect
to TP (#10 pin)
of PCB 0055 and
ground
VR3O2 19 kHz
lf you did not obtain -30 dB readings in steps 2 and 3 (compared with step 1), readjust VR301 until you obtain -30 dB
reading for both steps 2 and 3.
INDICATOR ADJUSTMENT REMAR KS
DC Voltmeter VR601 a. bAdjust for 0.005 V - 0.015 V across
R623 a, b with no signal

LEVEL DIAGRAM
AUX : FM: AM SELECTOR
ctr
=,
=50
=
C9
UJ
(9 40
O
30
FRE0UENCY AT. 1 kHz
16.7V
35W/8s,
o
E'
cl
I
V
o
E
6l
(o
co
PH(]NO INPUT
10