Realistic STA-21 Manuel utilisateur

STA.21

AM /FM STEREO RECETVER

Catalog Number : 31 -2071

cusT0M MANUFACTURED FOR RAD|0 SHACK [ln DMS|0N 0F TANDY C0RP0RAT|0N

(1} ELECTRICAL PERFORMANCE SPECIFICATIONS ..... 3 -

(2} DISASSEMBLY INSTRUCTIONS .

(3) BLOCK DIAGRAM

(4) ALIGNMENT INSTRUCTIONS .,. 7 -

(5) TROUBLE SHOOTING . . , 12 -

(6) DIAL STRINGING DIAGRAM

(7) IC & TRANSISTOR LEAD IDENTIFICATION .

(8) AM/FM TUNER, IF & MPX ASSEMBLED BOARD

(TOP & BOTTOM VIEWS)

(9) PRE & TONE AMP ASSEMBLED BOARD

(TOP & BOTTOM VIEWS)

(10) MAIN AMP & POWER SUPPLY ASSEMBLED BOARD

(TOP & BOTTOM V|EWS) ....... 18

(11) JACK ASSEMBLED BOARD

(TOP & BOTTOM VTEWS) ....... 19

(12) ELECTRICAL PARTS LIST . , . ,. 19 - 27

(13) EXPLODED VIEW PARTS LIST . 28 - 30

(14) IC INTERNAL DIAGRAM ...... 31

(15) SCHEMATIC DIAGRAM . 32 - 33

(16) EXPLODED VIEW 34 - 35

-2-

1. ELECTRICAL PERFORMANCE SPECIFICATIONS

AM BAND

Range

Antenna Sensitivity for S/N 20 dB

at 600 kHz

at 1000 kHz

at 1400 kHz

Terminal Sensitivity (20 dB S/N)

ACA at S/N 6 dB sensitivity at 1000 kHz

AGC Distortion at 1000 kHz, 100 mV/m, 80% Mod.

AGC Figure of Merit

lF Rejection at 600 kHz

lmage Rejection at 1400 kHz

Distortion at 5 mV/m 30% Mod.

Tapeout Level at 5 mV/m 30o/o Mod. 400 Hz

Fidelity 5 mV/m lnput, -6 dB Down (1 kHz:0 dB)

Whistle Modulation of 2nd and 3rd Harmonic

atland5mV/m

Calibration Accuracy at 600 kHz

at 1400 kHz

FM BAND

Range (For UL and C.S.A. Models)

Range (For European and Australian Models)

IHF Sensitivity at 90, 98 and 106 MHz

FM S/N Ratio at 98 MHz, 1 mV lnput

FM Limiting -3 dB

lF Rejection at 90 MHz

lmage Rejection at 106 MHz

Capture Ratio

ACA + 400 kHz at 100 pV

Audio THD 400 H2,75 kHz Dev.

Audio THD 400 H2,22.5 kHz Dev.

Calibration Accuracy at 90 MHz

at 106 MHz

AFC Holding Range with 1 mV Signal

AM Suppression

Maximum Signal Handling Capacity

Tapeout Level 1 mV 75 kHz Dev. 400 Hz Mod.

All Sets must meet the Requirements of the FCC.

UNIT

(kHz)

I pV /ml

( zV)

(dB)

(o/ol

(dB)

l'/ol

(mV)

(Hz) 50

(o/ol

(kHz)

UNIT

(MHz)

(l.VlHz)

(MHz)

( pYl

(dB)

( pV)

(dB)

lo/ol

(o/ol

(kHz)

(dB)

(v)

(mV)

NOM INAL

510 - 1650

455

200

1.5

250

- 2500

LIMIT

520 - 1620

500

s00

NOMINAL LIMIT

86.5 - 108.5 88 - 108

87.5 - 108.5 87.5 - 108

10.7

2.8

3.2

0.5

0.3

+ 200

0.2

750

3.5

200

t25

+50

;:;

7.1

1.0

0.8

t 500

+ 500

300 - 800

0.1

750 + 2.5 dB

Frequency Response must meet the 75 1-usec.De-emphasis for UL and C.S.A. Approved Models

(50 p sec.De-emphasis for European and Australian Models).

-3-

FM MPX

Stereo lndicator "ON" Point

Separation at 1 mV 100 Hz

1 kHz

10 kHz

Stereo Distortion 1 mV 1 kHz

38 kHz Rejection

SCA Rejection

AUDIO SECTION

lnput lmpedance PHONO MAG.

AUX

Output Power at THD 1% 8 ohms

Both Channels Driven at 1 kHz

Power Bandwi<ith B ohrns Both Channels Driven

TH D 1 o/o, 20 Hz - 20 kHz

Sensitivity for Rated Power

PHONO MAG.

AUX

Tape ln

Frequency Response at AUX (1 W t 2 dB)

Bass Action at 100 Hz

Treble Action at 10 kHz

Min. Volume Hum and Noise

Max. Volume Hum and Noise Tone Max. at AUX

Signal to Noise Ratio

PHONO MAG. 5 mV Input (lnput Short)

AUX 200 mV lnput

Cross Talk at 1 kHz AUX

Bass Compensation at 100 Hz -30 dB Volurne

Treble Compensation at 10 kHz -30 dB Volume

Tapeout Level PHONO MAG. at 3 mV 1 kHz

AUX at 200 mV 1 kHz

PHONO MAG. Eq. Response at 100 Hz

at 10 kHz

Tapeout Level (DlN Connector)

AM 5 mV,/m lnput 30% Mod.

FM 1 mV lnput 22.5 kHz Dev.

AUX 200 mV lnput

PHONO MAG. Overload

NOTE:

UNIT

( ,,rV)

(dB)

lo/ol

(dB)

UNIT

(K ohm)

(w)

(mV)

(Hz) 15

(dB)

(mV)

(dB)

(mV)

(dB)

(mV)

NOMINAL

0.6

LIMIT

2.0

NOMINAL

100

8.5

2.5

150

't50

-30K

+10

200

+13

-13

LIMIT

8.5

3.5

200

20-20K

t 10 t2.5

t 10 +2.5

+9 +2

+4 X2

200 + 2dB

+13 +2

-13 +2

25 + 3dB

25 t 3dB

The supply voltage is 120 volt AC (for UL and C.S.A. Models) (use 220/240 volt AC for European

and Australian Models), from a regulated power supply. The Power Source must insulated from

other equipment connected to antenna or output. The room temperature is 25 degrees C.

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 Specs.

-4-

2. DISASSEM BLY I NSTR UCTIONS

1)To remove chassis from wooden

cabinet.

Turn the cabinet upside down and

remove the five Pan head screws from

the cabinet bottom.

2) Removal of front panel (Aluminum

panel )

a) Remove the chassis from wooden

cabinet as described in 1).

b) Pull out the main chassis.

c) Remove the two Pan head screws from

the top and the three Pan head screws

from the bottom of the front panel.

d) Remove knobs and pull off panel.

3) To remove rear panel from chassis.

Remove the four Pan head screws from

the rear panel.

-5

3. BLOCK DIAGRAM

;P L

;; =i

aa >E

oo Io

";o

Zz F

O-O

6"HH

d<FF

t_l

il,

ftN

a>o

-z

>= !2o

?"3

uF"

":5

=*L

-6-

4. ALIGNMENT INSTRUCTIONS

MAIN AMPLIFIER AND RESET CIRCUIT ADJUSTMENT/CHECK

NOTE o Maintain line voltage at 120 volts. (UL, C.S.A.) (Use 220/240 VAC For European & Australian Models.)

o Set SELECTOR Switch to AUX.

. Set MODE Switch to STEREO.

o See P.C.B. illustrations for alignment points/adjustments.

MAIN AMPL!FIER ADJUSTMENT

STEP ADJUSTMENT EOUIPMENT CONNECTION AUDIO FREO. LEVEL ADJUSTMENT

Check DC Balance

by measuring

DC voltage

across Output

of L and

R channel.

DC Volt Meter See Fig. 1No signal DC

voltage

should be

less than

30 mV.

Select of

8305(L channel)

R306(R channel)

ldling current

adjustment DC Volt Meter See Fig,2 No signal Adjust voltage

across Emitter

resistors R321

and R322

to 10 mV.

(8 0 Load)

R329

R330

0-30 mV

Main Amp Figure 1 (-30 mV to +30 mV)

Reset Lamp

8 ohm load

Speaker Output Oscilloscope (When protector circuit is activated)

Oscilloscope

Osc

Hz)

Adjust Volt Meter for 10 mV

Main AmP Figure 2

RESET CI RCU IT ADJ USTM ENT

STEP ADJUSTMENT EOUIPMENT CONNECTION AUDIO FREO. SETTING LEVEL ADJUSTMENT

1Turn trimmer resistor R 332 counterclockwise (minimum value).

Audio Osc.

V.T.V.M. Figure 31000 Hz VOLUME: Max

BASS, TREBLE

& BALANCE:

Center

Adjust input to

AUX 1 to get

output level

of about 3 Volts

(8 ohm load)

Reset circuit

adjustment Audio Osc.

V.T.V.M. Figure 41000 Hz Same as

above Adjust R 332 so

output drops to zero

(RESET comes "on")

when output speaker

terminals are shorted:

DO NOT ADJUST

PAST THIS POINT.

R 332

Figure 3

-7 -

AC V.T.V.M. (3V) Figure 4

@l-"o'" "o'''''ou'

(TC 1O3)

FM OSC, TRIMMER

[mAN___r%3i*,

ta_\

Elf- FM lsr lF rr rolr

ALIGNMENT

Signal generator output should be no higher than necessary to obtain an output reading.

Maintain line voltage at 120 volts. {UL, C.S.A.} (Use 220/240 VAC For European & Australian Models.)

Set SELECTOR Switch to AM.

See P.C.B. illustrations for alignment points/adjustments.

AM ALIGNMENT SET-UP

AM INTERNAL BAR ANTENNA Scope

Figure 5

-8-

EOUIPMENT REOUIRED

1. AM Signal Generator

2. AC Voltmeter

3. Oscilloscope

AM IF&

NOTES:

TUNER COIL

rrc 101) (rc 104]

FM ANT AM ANT

TRIMMER TRIMMER

& TRIMMER LOCATIONS

(TC 102) (TC 1O5)

FM RF AM O$,

TRIMMER TRIMMER

STEP SIGNAL GENERATOR

COUPLING SIGNAL GENERATOR

FREOUENCY DIAL SETTING INDICATOR ADJUSTMENT REMARKS

Connect standard

loop ANTENNA to

Signal Generator

and radiate signal

into the AM Ferrite

antenna. See Fig. 5.

455 kHz

(4ob Hz,30% MoD) Point of non-

interference

(near 600 kHz)

AC Voltmeter

tO TAPE OUT

JACK

T 106

1 107

T 108

T 109

Adjust for

maximum

reading.

2Same as above 600 kHz (400 Hz,

30o/o MOD) 600 kHz Same as above T 105 (OSC Coil)

L 106 (AM ANT

Coil)

Adjust for

maximum

reading.

Same as above 1400 kHz (400 Hz,

30o/o MOD) 1400 kHz Same as above TC 105

(OSC Trimmer)

TC 104

(ANT Trimmer)

Adjust for

maximum

reading.

4Repeat steps 2 and 3 urrtil no further change is noticed.

Same as step 'l 1000 kHz (400 Hz,

30% MOD)

Output level

to 100 mV,/m

Point of non-

interference

and no signal

AM Strength

Meter Select

value of

R 160

Meter Pointer

on Receiver

should indicate

between 80o/o

and 90% on

the Meter.

AM SIGNAL GENERATOR 2'(60cm)- tlr)r'\

VOLTMETE R@

Cf)B---

[.=-rE[!--=

STA-21

TAPE OUT (L or R)

FM RF & IF ALIGNMENT

EOUIPMENT REOUIRED 3. AC Vottmeter

1. FM signal Generator output Level: 1 mV 4. oscilloscope

2. Sweep Generator S. Distortion Meter

NOTE o Signal Generator output should be no higher than necessary to obtain an output reading.

. Set SELECTOR Switch to FM.

o Maintain Line voltage at 12Q volts. (UL, C.S.A.) 1220/240 VAC For European & Australian Models.)

a Refer to P.C.B. illustrations for test points,/adjustments.

STEP GENERATOR

COUPLING GENERATOR

FREOUENCY RADIO DIAL

SETTING INDICATOR ADJUSTMENT REMARKS

Sweep Generator to

"FM ANT" terminal

on FM Front end

board

10.7 MHz

(1400 kHz

Sweep)

Any dial setting

where no noise

or interference

exists

Scope to TP 7

at R 151

{MPX input)

AM/FMIMPX

Board

T 101, 102

103, 104

(Primary)

FM IFT

Adjust for maximum

amplitude and

proper linearity

between + 150 kHz

markers.

Refer to Fig. 7.

Sweep Generator to

FM Antenna

Terminal thru FM

Dummy antenna

(300 ohm)

T101, 102

FM IFT

Same as above T 104 FM IFT.

(Primary and

Secondary)

Ajust for symmetri-

cal "S" curve as

shown in Fig.6.

Signal Generator to

FM Antenna

Terminal thru FM

Dummy antenna

(300 ohm)

98 MHz

(400 Hz, 100o/o

MOD}

Tune for

Maximum

reading on

meter

Distortion

Meter to TAPE

OUT Jack

T 104

FM Discrim.

(Secondary)

Adjust for minimum

distortion.

Same as above *86.5 MHz

See Note

in step 7

Tuning gang

fully closed AC Voltmeter

and Scope to

TAPE OUT

Jack

L 105

(FM OSC} Adjust for maximum

reading on meter.

6Same as above 108.5 MHz Tuning gang

fully opened TC 103 (FM

OSC Trimmer)

7Repeat STEPs (5) and (6) until Tuning Range Covers exactly from 86.5 MHz to 108.5 MHz.

(*European models must not be able to tune below 87.8 MHz.)

Signal Generator to

FM Dummy

antenna (300 ohm)

90 MHz 90 MHz

Tune to

Signal

AC Voltmeter

and Scope to

TAPE OUT

Jack

L 101

(FM ANT Coil)

L 103 (FM BF

Coil; stretch

or squeeze)

Adjust for maximum

reading on meter.

Same as above 106 MHz 106 MHz

Tune to

Signal

TC 101 (FM

ANT Trimmer)

TC 102 (FM

RF Trimmer)

10 Repeat STEPs (8) and (9) until no further improvement is noticed.

11 Same as STEP (8)

ANT. input: 1 mV 98 MHz 98 MHz Tune to

Signal T110 Adjust for maximum

reading on meter.

12 Same as STEP (8)

ANT. input: 100 mV VR1Ol Adjust so the Meter

Pointer on Receiver

is full scale.

-9-

FM SIGNAL GENERATOR

FM ALIGNMENT SET-UP

3OOO DUMMY FM ANT

Sweep Gen-

FM STEREO ALIGNMENT

Equipment Required

1. Stereo Modulator . . .. .

2. FM Signal Generator . .

3. Audio Generator

4. AC Voltmeter

5. Oscilloscope

6. Distortion Meter

7. Frequency Counter

Note: See P.C.B. illustration for alignment/test points.

Preliminaries

Set SELECTOR switch to FM STEREO.

MULTIPLEX & SEPARATION ALIGNMENT

TAPE OUT

(L or B)

AC V.T.V-M- DISTOBTION METER

tLrpTatRlsl(470)

Figure 7

Connect Stereo Modulator to EXT. Mod. terminal FM signal generator.

Modulation Level of 19 kt{z Pilot Signal ....8 - 10 %

Output Level ... 1 mV

Frequency ....... Approximately 98 MHz

Deviation ........75 kHz 100 % modulation of composite signal

STEP SIGNAL GENERATOR

COUPLING STEREO

MODULATION INDICATOR ADJUSTMENT REMARKS

Connect to FM Antenna

terminal thru FM

dummy antenna(30O 0 )

Mono. 1 kHz

{1000 Hz, No Mod)

lnput 1 mV

Counter connected

to TP 14 at Pin No 12

of lC

VR 103 Adjust for 19 kHz

+50 Hz on Counter.

Refer to Fig. 8.

Same as above Composite MPX

Signal 1 kHz on

Left channel ONLY

AC Voltmeter

connected for

TAPE OUT

jack of Right

channel

VR 102

(Separation) Adjust for mini-

mum reading.

Refer to Fig. 9.

Same as above Composite MPX

Signal 1 kHz on

Right channel ONLY

AC Voltmeter

connected for

TAPE OUT

jack of left

channel

Same as above Same as above

4Repeat STEPs 2 and 3 until AC Voltmeter reading is at least -33 dB re same channel output (i.e.

33 dB separation).

Same as step 1Composite

Signal 1 kHz AC Voltmeter

connected to

TAPE OUT

jack

With 10 pV

antenna input signal,

stereo indicator

lamp should come on.

- 10-

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