Realistic STA-235 User manual

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V
STA.235
AM IFM STEREO
Catalog Number: RECEIVER
31-2065
cusToM MANUFACTURED FoR RADIo sHAcKIn DrvrsroN 0F TANDv coRpoRATroN
I

CONTENTS PAGE
1. SPECIFICATIONS 3- 4
2. BLOCK DIAGRAM ........ 5
3. DISASSEMBLY INSTRUCTIONS ......... 6
4. DIAL STRINGING DETAIL .............. 6
5. ALTGNMENT PROCEDURE ........ ........... 7 - I
6. ALIGNMENT POTNTS ......... ....... 10
7. LEVEL DTAGRAM .................... 11
8. TROUBLESHOOTTNG ........... 12- 19
9. 5030 EO AMp BOARD ............. ................... 19
10. 0042 TUNER BOARD ................ 20
11. OO43 TONE AMP & AUTO-M BOARD .,...,.. 21
12. OO45 MAIN AMP BOARD .,.,.,,,. 22
13. 6044 AUDIO DRIVER AMP BOARD ......... 23
14. 8030 POWER SUPPLY BOARD .................. 24
15. TRANSTSTOR & tC LEAD tDENTtFtCAT|ONS............... ............... 25
16. ELECTRICAL PARTS LIST 26 - 33
17, MISCELLANEOUS PARTS LIST ........ .,...,,.. 34
18. SCHEMATIC DIAGRAM ............. SEPARATE SHEET
19. EXPLODED VIEW SEPARATE SHEET

SPECIFICATIONS
NOMINAL LIMIT UNIT
1.
2.
FM SECTION
TUNING RANGE
DIAL CALIBRATION ACCURACY 90 MHz
98 MHz
106 MHz
USABLE SENSITIVITY
(NOISE & DISTORTION -30 dB)
IMAGE REJECTION (at 106 MHz)
lF REJECTION (at 90 MHz)
FULL LIMITING (at -3 dB)
lF BANDWIDTH (6 dB down)
DISTORTION (1mV INPUT)
SIGNAL-TO-NOISE RATIO (1mV INPUT)
DE-EMPHASIS 75 psec. (at 50- 10,000 Hz)
DISCRIMINATOR BANDWI DTH (Peak-to-Peak)
AFC HOLDING RANGE (with 1 mV signal)
OI.,'TPUT VOLTAGE
(at 75 kHz dev., 4OO Hz mod., 1
MUTING THRESHOLD
OVERLOAD. THD at 98 MHz, 100%
(100 mV RF input)
SPURIOUS RESPONSE at 98 MHz
ANTENNA INPUT 3 pV,1/21F, 103.35 MHz
CAPTURE RATIO (1 mV INPUT)
ALTE RNATE CHANNE L SE LECTIVITY
(1 mV input)
3.
4.
5.
6.
7.
8.
L
10.
11.
12.
13.
14.
15.
16.
17.
18.
mV input)
mod.
MPX SECTION
1. STEREO SEPARATION
(1OOo/o mod., 1 mV input) 100 Hz
1 kHz
10 kHz
2. DISTORTION 1 kHz
(100% mod., 1 mV input)
3. STEREO BEACON SENSITIVITY (pilot 7%)
4. RESIDUAL 19 kHz & 38 kHz ('l mV input)
5. SUPPRESSION OF SCA INTERFERENCE
(1 mV input)
AM SECTION
3.
1.
2.
4.
5.
6.
TUNING RANGE
DIAL CALIBRATION ACCURACY 600 kHz
1,000 kHz
1,400 kHz
USABLE SENSITIVITY 600 kH2,1000 kHz, 1400 kHz
(4OO H2,30% mod., Radiated
noise & distortion -20 dB) Direct
IMAGE REJECTION (at 1,400 kHz)
lF REJECTION (at 600 kHz)
AGC FIGURE OF MERIT
(from 100 mV/m at 1,000 kHz)
DISTORTION
(4OO H2,30% mod., 10 mV/m input)
lF BANDWIDTH (6 dB down)
OUTPUT VOLTAGE
(400 H2,30% mod., 5 mV/m input)
7.
8.
9.
87.5-108.5
2.O
75
100
1.5
0.2
70
r 1.5
400
t 1,000
0.9
8
0.5
80
2
75
510-1 700
40
40
30
0.5
4
55
250
20
7A
60
45
0.8
18
300
88-108
t25O
t350
t25O
3.0
65
80
2.O
t'150
0.8
60
x2.O
300
t800
0.9r3 dB
3-16
1.0
70
3.5
60
25
30
20
1.0
3-16
45
40
520-1620
t15
t30
t40
40
2.0
13-26
200
400
30
58
50
MHz
kHz
kHz
kHz
pV
dB
dB
pV
kHz
o/
/o
dB
dB
kHz
kHz
o/
/o
dB
dB
dB
dB
dB
dB
V
pV
o/
/o
pV
dB
dB
kHz
kHz
kHz
kHz
pVlm
pV
dB
dB
dB
o/
/o
kHz
mV

NOMINAL LIMIT UNIT
10. AUDIO RESPONSE
(5 mV/m input from 400 Hz to 2 kHz,0 dB
@ 1,000 kHz)
11. SELECTIVITY 2OOpVlm
12, SIGNAL-TO-NOISE RATIO
(1,000 kHz, with antenna input 5 mV/m)
13. AM BEAT (input 5 mV/m)
14. WIDE BAND AM THRESHOLD
AUDIO SECTION
1. RMS OUTPUT POWER
(distortion 1. O.3o/o, 20 Hz - 20 kP'zl
PER CHANNEL DRIVEN 8 O
4a
BOTH CHANNELS DRIVEN 8 O
4a
2. IM DISTORTION
(at 40 W output 7Ol7,OOO Hz 4l1l
3. HARMONIC DISTORTION (at 40 W output)
100 Hz
1,000 Hz
4, FREOUENCY RESPONSE 1O,OOO HZ
(AUX, 8 o load, 1 W output, t1.0 dB)
(AUX, 8 c| load, 1 W output, +1.5 dB, -4 dB)
5. INPUT VOLTAGE (at 50 W output)
PHONO-HI
PHONO-LO
AUX
TAPE MONITOR
PHONO MAG
AUX
TAPE MONITOR
BASS 100 Hz
MIDRANGE 1.5 kHz
TREBLE 10 kHz
8. EOUALIZATION RIAA: 30- 15,000 Hz
9. PHONO AMP OVER LOAD CAPABILITY (at 1% HDI
HI
LO
HIGH FILTER
LOW FILTER
LOUDNESS COMPENSATION (Volume -30 dB)
50 Hz
100 Hz
13. CHANNEL SEPARATION
(AUX input 100 - 10,000 Hz)
14. SIGNAL-TO-NOISE RATIO (input shorted)
PHONO MAG
AUX
15. RESIDUAL NOISE
16. LOAD IMPEDANCE
17. POWER SOURCE 120 Volts,60 Hz AC*
30 WATTS, No Signal
320 WATTS, Full Signal
22O|24OV AC, 50 Hz for European and Australian Models
6. INPUT IMPEDANCE
7, TONE CONTROL
10.
11.
12.
10 kHz
70 Hz
-3
25
40
3
70
65
60
65
0.1
0.03
0.03
0.08
50-30k
20-70k
5
2.5
210
210
50
70
70
t8
t6
r10
100
200
-6
-6
11
I
40
65
80
0.5
32
10
10-50
-6
20
60
55
55
55
0.3
0.15
0.15
0.3
20-40k
5t1
2.St0.5
21 et30
219t30
t8t2
x6t2
x1Ot2
RIAAl2
80
160
-Gt2
-6x2
11t2
9x2
35
58
70
1.5
4-16
dB
dB
dB
o/
/o
mV
W
W
W
W
o/
/o
o/
/o
o/
/o
o/
/o
Hz
Hz
mV
mV
mV
mV
ke,
kr,
k(?
dB
dB
dB
dB
mV
mV
dB
dB
dB
dB
dB
dB
dB
mV
OHM
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 stiil might be considered acceptable; in no case should a unit perform
to less than within any Limit Spec.

BLOCK DIAGRAM
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ts r +vl
9
55
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E9HS3P;
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D!SASSEMBLY I NSTRUCTIONS
1. Removing chassis from Wooden Cabinet. (Refer to the Fig. A.)
Remove five screws-two (BB) from each side of the wooden cabinet and one(89)
from the back.
2. Removing the front Panel. (Refer to the Fig. A.)
Remove six screws-three (89) from each side of the Front Panel and remove
panel.
6B-_ )
-aq @\o*@
Fig. A
DIAL STRINGING DIAGRAM
Note: Tuning capacitor should be in fully closed position'
NO SHAFT
DIAL DRUI,/

ALIGNM ENT PROCEDURES
Do not attempt alignment unless the following equipment is available.
1. AM Signal Generator
2. Oscilloscope
3. AC Voltmeter
Note: Remove line cord antenna from FM external antenna terminal when aligning.
AM IF & RF ALIGNMENT
4. FM Signal Generator
5. Stereo Modulator
6. Audio Generator
RECEIVER
7. Distortion meter
8. DC Voltmeter
9. Frequency Counter
TAPE OUT
Output of signal generator should be no higher than necessary to obtain an output reading.
Signal Generator Modulation: 30%
Set SELECTOB switch SW1 to AM.
STEP SIGNAL GENERATOR
COUPLING
SIGNAL
GENERATOR
F R EOU ENCY
RECE IVER
DIAL
SETTING INDICATOR ADJUSTMENT
Refer Fig. 4. REMARKS
1Refer Fig. 1455 kHz
(400 Hz Mod.)
Point of non-
i nterfe re nce
(on/about
600 kHz)
AC Voltmeter
to TAPE OUT
jack CF4O1
(Both Sections) Adiust for maxi-
mum reading.
2Same as Step 1600 kHz
(400 Hz Mod.) 600 kHz Same as Step 1
L401
(RF COIL)
L402
(OSC. COIL)
L451
(ANT. COIL)
Same as Step 1
3Same as Step 11400 kHz
(400 Hz Mod.) 1400 kHz Same as Step 1
TC1 O5
(ANT. Trimmer)
TC1 06
(RF Trimmer)
TC1 07
(OSC. Trimmer)
Same as Step 1
4Same as Step 11000 kHz
(400 Hz Mod.) 1000 kHz Same as Step 1VR4O3
Adjust for 300
mV on AC
Voltmeter with
input of 5 mV/m.
5Same as Step 11000 kHz
(4 kHz Mod.) 1000 kHz Same as Step 1VR4Ol
Adjust for 21O
mV reading on
AC Voltmeter
with input of
28 mV/m.
6Same as Step 11000 kHz
(400 Hz Mod.) 1000 kHz SIGNAL
Meter VR4O2
Adjust for 80%
reading of full
scale with input
of 5 mV/m.
Note: Remove line cord antenna from FM external antenna terminal when aligning.
TUNER
FRONT END
TC105, TC106,
TC1 07
L401, L402
AM/FM IF
cF401
Fig. 1 AM ALIGNMENT CONNECTION

FM RF AND IF ALIGNMENT
Signal generator output should be no higher than necessary to obtain an output reading.
Set Selector switch to FM.
Signal Generator deviation: 75k1z NOTE: Be sure to disconnect FM line cord antenna during alignment.
STEP SIGNAL GEN E RATOR
COUPLI NG
SIGNAL
GENERATOR
F R EOU ENCY
RECEIVER
DIAL
SETTI NG INDICATOR ADJUSTMENT
Refer Fig. 4. R EMAR KS
1
Connect to FM
Antenna Termi-
nal through
FM Dummy
Antenna
(300C2). Fig. 2
90 MHz
(400 Hz Mod.) 90 MHz AC Voltmeter
connected to
TAPE OUT
jack
L1 01
(ANT. COIL)
L102
(RF COIL)
L1 03
(RF COIL)
Ll 04
(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 02
(RF Trlmmer)
TC103
(RF Trimmer)
TC1 04
(OSC,Trimmer)
TCi O1
(ANT.Trimmer)
Same as Step 1
Repea steps 1 & 2 until no furtherimprovement is possible.
3Same as Step 190 MHz
(400 Hz, Mod.) 90 MHz Same as Step 1T1 01
(FM IFT} Same as Step 1
4Same as Step 190 MHz
(400 Hz, Mod.) 90 MHz
DC Voltmeter
connected to
Pin #16 and
#17 on PCB
#oo42
L203
(Pink Core)
Adjust for zero
reading on DC
Voltmeter.
5Same as Step 190 MHz
(400 Hz, Mod.) 90 MHz
Distortion
Meter con-
nected to
TAPE OUT
jack
L203
(Blue Core) Adjust for mini-
mum distortion.
6Same as Step 198 MHz
(400 Hz, Mod.) 98 MHz Same as Step 1vR202
Set SE LECTOR
switch to FM
MUTE. Adjust
for zero reading
on AC Voltmeter
with SG output
level of 4 pV.
7Same as Step 198 MHz
(400 Hz Mod.) 98 MHz SIGNAL
Meter VR201
Adjust for Full
Scale of SIGNAL
Meter with SG
output level of
2 volts.
For European model, the lowest frequency of FM tuning range should not be below 87.5 MHz.
125{7 nD.5{l,1 FM Dummy Antenna to 300 Cl antenna terminal of Receiver
1 50,f}
Zin = 50sl (75o) Zout = 3O0O (balanced)
Fig. 2 FM DUMMY ANTENNA

M PX ALIGNM ENT TAPE OUT
FM ANTENNA
TERMINAL
(300s,) RECEIVER
TUNER
FRONT END
L101, L102
L103, L104
T1 01 . TCl 01
TC1 02, TC1
TCl 04
FM SIGNAL
GENERATOB FM DUMMY
ANTENNA
300rl MPX
VR30,I
V R3O2
STEREO
MODULATOR
___l
Fis.3 MPX ALIGNMENT CONNECTION
lf you did not obtain -30 dB readings in steps 3 and 4 (compared with step 2), readjust VR301 until you obtain -30 dB
reading for both steps 3 and 4.
MAIN AMPLIFIER ALIGNMENT
Set SELECTOR Switch to FM.
Tune for 98 MHz on band.
Signal Generator output level: 1000 trrV Deviation: 75 kHz at 1OO% modulation of composite signal
connect Signal Generator to FM Antenna Terminal through FM Dummy Antenna (300 o).
STEP
19 kHz
(PILOT SIGNAL)
MODULATION
Level
SIGNAL
GENERATOR
Freq. Set to
OUTPUT
INDICATOR
Connected to
ADJUST
Refer
Fis.4. ADJUST
FOR NOTE
1
Frequency counter
connected to TP3
and Ground VR3O2 76 kHz
29Yo Composite 1 kHz
R channel
AC Voltmeter
connected to
TAPE OUT jack
of R channel
Adjust input
for Audio output
of about 0.9V.
38Yo Composite 1 kHz
L channel
AC Voltmeter
connected to
TAPE OUT jack
of R channel
VR301 mtntmum
AC Voltmeter
reading should
be at least 30
dB below read-
ing in step 2.
48Yo Composite 1 kHz
R channel
AC Voltmeter
connected to
TAPE OUT jack
of L channel
VR301 mtntmum Same as Step 3
INDICATOR ADJUSTMENT REMARKS
DC Voltmeter VR601a, bAdjust for 0.005-0.015 volts across
R626a, b with no signal.
I

ALIGNM ENT POINTS
VR4O1 VR302
1451 ,/. w
.:,',:?..
t?
,
a
@il'.'.-...;;
&:;::,.:::ir:1r:::it t:,
t
VR6O1a L203
Figure 4
vR601 b
10

LEVEL DIAGRAM
FILTER FILTER
@
z.
z.
(9
U
(,
F
J
o
FREOUENCY : 1 KHZ
INPUT
SELECTOR
6
E
st
+
(Low) |
2.5mV I
11

TROUBLESHOOTING
Symptom Cause and Remedy
1 ) Receiver not operative:
Pilot lamp does not light. A) Faulty AC power cord
Replace the cord.
B) Defect in the power switch
Replace the switch.
C) Broken wire in the power transformer
Rep lace the transformer.
D) Broken power fuse
Replace the fuse.
2l Fuse blows when power is
turned on. A) Power Transformer T851 defective
Replace the transformer.
B) Short in the primary or secondary of the trans-
former circuitry
Repair the short.
C) Damaged rectifier D807
Replace the damaged rectifier.
D) Short circuit in the rectif ier circuit
Repair the short.
E) Short circuit in the power transistor TR608a, b or
TR609a, b
Replace the defective transistor and check circuit.
3) Pilot lamp does not light. A) Defective lamp
Replace lamp.
B) Disconnection in the transformer T851 tertiary
winding
Replace the transformer.
4l Pilot lamp lights but no sound
from both channels. Resistor R814, R809. R923 or R924 open
Replace.
Capacitor C803, C804, C805, C812, C813, C851,
C852, C916 or C917 defective
Replace the defective capacitor(s).
Diode D807 damaged
Replace the diode.
Open in secondary winding of the power trans-
former T851
Replace the transformer.
Transistor TR804 or TR806 open
Replace the transistor(s).
Diode D802, D804 or D805 damaged
Replace the damaged diode(s).
Defective D801 or D803
Replace the defective diode(s).
A)
B)
c)
D)
E)
F)
G)
12

Symptom Cause and Remedy
H) Transistor TR803 defective
Replace the transistor.
l) Defective R802, R803, R804, C801 or C802
Replace the defective component(s).
J) Defective Relay RL801
Replace.
5) A Speakers do not work. A) Speaker switch 51 defective
Replace the switch.
6) B Speakers do not work. A) Speaker switch 51 defective
Replace the switch.
7l One channel does not work with
VOLUME at maximum with a
test signal applied to the center
terminal of VOLUME control
VR951 of the dead channel.
A)
B)
Defect in transistor TR901, TR902 or TR903 of
TONE AMP BOARD OO43
Locate and correct the defect.
Defect in transistor TR601, TR602, TR603, TR604,
TR605, TR606, TR607, TR6O8, TR609 or TR610
of MAIN AMP DRIVER and MAIN AMP BOARD
0045
Locate and correct the defect.
C) Break in copper foil of printed circuit board 6044,
0043 or 0045
Repair or replace circuit board.
Short in speaker output terminal
Repair the short.
Defective resistor R901, R902, R903, R904, R905,
R906, R907, R918, R919, R920, R737, R738,
R742, R602, R603, R604, R605, R606, R607,
R608, R609, R610, R612, R613, R614, R615,
R616, R625, R626, R621 or R622
Replace the defective resistor(s).
D)
E)
8) Same as 7 above but channel
operates when test signal is
applied as 7.
A) Defective SELECTOR switch 52 or TAPE
MONITOR 1 and2 switches 53, 54
Repair or replace the switch(es).
9) Speaker works normally but
headphones do not work. A) Headphone plug does not mate with jack
Replace the plug.
B) Defective resistor R651a, b
Replace the resistor(s).
10) All inputswork normally
except for AUX input. Poor contact in AUX input jack
Repair or replace the jack.
Faulty SELECTOR switch 52
Repair or replace the switch.
A)
B)
13

Symptom Cause and Remedy
11) PHONO input not operative A) Defective 1C501
Replace the lC.
B) Faulty resistor R501, R502, R503, R504, R505,
R506, R507 or R508
Replace the faulty resistor(s).
C) Faulty capacitor C501, C5O2, C503, C504, C507
or C508.
Replace the faulty capacitor(s).
D) Poor contact in PHONO input jack
Repair or replace the jack.
E) Faulty SELECTOR switch 52
Repair or replace the switch.
12) TAPE MONITOR 112not
operative A) Defective contact in TAPE MONITOR 112 OUT
jack
Repair or replace the jack.
13) FM does not operate. A) Transistor TR808 damaged (open)
Replace the transistor.
Defective resistor R81 6
Replace the resistor.
Short circuit in TUNER B+ circuit
Repair the short.
Poor contact in SELECTOR switch 52
Repair or replace the switch.
Resistor R301 defective
Replace the resistor.
Choke coil L2O2 defective
Replace the choke coil.
Capacitor C301 defective
Replace the capacitor.
Defective lC 1C201 or lC2O2
Replace the defective lC('s).
Defective IFT T101 or Coil L203
Replace the defective component(s).
Defective resistor R201, R203, R204, R205, R216,
R217, R218, R221, R222, R225 or R232
Replace the defective resistor(s).
Defective capacitor C111, C112 or C2O1
Replace the defective capacitor(s).
Defective transistor TR101 ,TR1O2, TR103 or coil
1101-L105 of TUNER BOARD 0042
Replace the defective component(s).
Faulty lead-in
Repair or replace the lead-in.
B)
c)
D)
E)
F)
G)
H)
t)
J)
K)
L)
M)
€
14

Symptom Cause and Remedy
14], Poor multiplex separation A) lmproper adjustment
Readjust T101, VR301 and VR302.
(Refer to MPX ALIGNMENT on page g.)
B) Transistor TR301, TR302, TR303 or lC 1C301 of
TUNER BOARD OO42 defective
Replace the defective component(s).
C) Variable resistor VR301 or VR302 defective
Replace the defective variable resistor(s).
15) Stereo indicator does not light. A) Defective indicator LED D756
Replace the LED.
B) lmproper adjustment of VR301 of TUNER BOARD
oo42
Make readjustment.
(Refer to MPX ALIGNMENT on page 9.)
C) Defective lC 1C301 or resistor R327
Replace the defective component(s).
16) FM volume not sufficent A) lf volume of both L and R channels not enough:
Front-End defective, or faulty I FT T101 or diode
D2O7, D208 or faulty lC lC2O2,lC301 or capacitor
C219 of TUNER BOARD 0042
Locate and replace the defective component(s).
B) lf sound of one channel not enough: Defective
LPF301 or TR302 (PCB 0042) in case of L channel,
or defective LPF302 or TR303 (PCB 0042) in case
of R channel
Replace the defective component(s).
17l. AM does not operate. Damaged either 1C401 or TR404 of TUNER
BOARD OO42
Replace the damaged component(s).
Def ective L4O1 , L4O2 or C F401 of TU N E R
BOARD OO42
Replace the defective component(s).
One of resistors of TUNER BOARD 0042 defective
Replace the defective one.
One of capacitors of TUNER BOARD 0042
defective
Replace the defective one,
SELECTOR switch 52 defective
Repair or replace the switch.
Defective Tuning Gang
Replace.
Damaged AM bar antenna
Repair or replace bar antenna.
A)
B)
c)
D)
E)
F)
G)
15

Symptom Cause and Remedy
18) LOUDNESS has no effect. A) Defective LOUDNESS switch 57
Replace the switch.
B) Defective capacitor C731 or resistor R735
Replace defective component( s).
C) Defective VOLUME control VR951
Replace.
19) STEREO-MONO not effective A) Defective MONO switch 56
Replace the switch.
2Ol TAPE MONITOR 1 or 2 not
effective. A) Defective TAPE MONITOR switch 53 or 54
Replace the defective switch(es).
B) Poor contact in TAPE MONITOR 1 or 2lN jacks.
Repair or replace jack(s).
211, BASS control has no effect. A) VR903 defective
Replace.
B) Defective capacitor C910, C91 1, C912 or resistor
R913, R914, R917 of TONE AMP BOARD 0043
Replace defective component(s).
221 MID-RANGE control has no
effect. A) VR902 defective
Replace.
B) Defective C908, C909, R911, R912 or R916 of
TONE AMP BOARD OO43
Replace the defective component(s).
23], TREBLE control has no effect. A) VR901 defective
Replace.
B) Defective C906, C9O7, C909, R910 or R915 of
TONE AMP BOARD OO43
Replace the defective component(s).
241, Excessive noise with PHONO
input A) Faulty 1C501
Replace the lC.
B) Faulty R501, R502, R503, R504, R505, C501 or
c503
Replace the faulty component(s).
251 Noisy VOLUME control A) Defective VR951
Replace the variable resistor.
B) Defective capacitor C508, C901, C9O4, C914 or
c602
Replace the defective capacitor(s).
26l. SIGNAL meter not functioning A) Defective meter
Replace the meter.
16

*
\t*
A
tri
Symptom Cause and Remedy
B) ln case of FM reception, R226, C210, C223, C251 ,
D203 or D204 defective
Replace the defective component(s).
C) ln case of AM reception, VR401 ,VR4O2, D401,
TR401 or TR4O2 defective
Replace the defective component(s).
271 AUTO-Magic AFC has no
effect when AUTO-M switch
is ON.
(White light behind the
tuning meter does not change
to red when the tuning control
is touched.)
A) Transistor TR701 ,TR7O2 or 1C701 defective
Replace the defective component(s).
B) Resistor R701-R718 defective
Replace the defective resistor(s).
C) Diode D701 or D702 defective
Replace the defective diode(s).
D) Capacitor C701-C704 defective
Replace the defective capacitor(s).
E) Defective switch S10
Replace.
F) Defective AUTO-Magic indicator lamp PL4
Replace the lamp.
28) White light does not light when
the tuning control is released. A) Defective transistor TR701 (short) f R7O2 (open)
or lC 1C701
Replace the defective component(s).
B) Defective resistor R703-R718
Replace the defective resistor(s).
29], OUATRAVOX not effective A) Defective switch 51
Replace the switch.
30) TONE F LAT has no effect. A) Defective switch 55
Replace the switch.
31) FILTER-LO has no effect. A) Defective switch 59
Replace the switch.
B) Defective capacitor C732
Replace the capacitor.
32) F I LTE R-H I has no effect. A) Defective switch 58
Replace the switch.
B) Defective resistor R738 or capacitor C733
Replace the defective component(s).
,:,rrWlDE BAND AM is not functioning.
"ol (Wh.n this circuit is functioning, hi-gh
frequency response (3 tHz and above)
will improve with high input signal levels.
With input level of 28 mV/m or more,
high frequency response should be
noticeably better. Use high quality sig.
gen. modulated with 3 kHz or 4 kHz.
A) Damaged transistor TR401 ,TR4O2 or TR403 of
TUNER BOARD OO42
Replace the damaged transistor(s).
B) Defective diode D401
Replace the diode.
b
$,
F
L.
r;"
17

Symptom Cause and Remedy
C) Damaged transistor TR404
Replace the transistor.
D) lmproper adjustment of VR401
Readjust V R401 .
(Refer to AM lF & RF ALIGNMENT on Page 7.) I
*
Note: 1. This Amplifier has built-in over load thermal protection for abnormal operation.
When the temperature of the thermal protector (installed with heatsink) does rise ab-
normally (90 I 5'C), the thermal protector will automatically cut out, and as soon as
the temperature goes down sufficiently (65 t 15'C), the thermal protector turns back
on automatically. lf the Receiver does turn itself off, check ventilation and speaker
connections,
FUSE
4A POWER SWITCH
Heat Sink of Output Transistor
POWER
TRANSFORMER AC Outlets
Figure 5
t
d
o
tu
-
O
F
=
a
z
f
Thermal Protector
18

2. Transistors TR605 and TR606 protects the audio output stage when abnormally high
current flows through TR608 and TR609, caused by excessive drive at input, or too
low impedance load is connected at output. lf increase of the current is excessive, the
voltage across R625 and R626 will turn on TR605 and TR606 which are normally not
biased " on" .
The collector potential of these transistors (through D601 and D602 diodes) reduce
bias on TR604 and TR607, which causes output transistor current (TR60B and TR609)
to reduce.
This performs two safety functions.
1 ) Protects the output circu it devices.
2l Protects the speakers from loud clicks, pops and excessive levels.
+Vcc
TO
DRIVE TR608
D601
CIRCU IT
TR605 OUTPUT
NF
CIRCUIT
I
Ji
&'
(o
N
(o
tr
l-
D602
*
TO
DRIVE
CIRCUIT TR609
-Vcc
f
#Figure 6
19

5O3O EO AM P BOARD (TOP V|EW)
5030 EO AM P BOARD (BOTTOM VIEW)
f
ri
,i
31
*: See page 35 for Change lnformation.