Philips FW2017 User manual

Service
Services
Service
Table of contents
Specification
Warnings
Connection & Controls
Wiring Diagram
Power Board
Circuit description
Component Layout
Circuit Diagram (Left / Right channel)
Component Layout
Circuit Diagram (Bass stage)
Front Panel
Component Layout
Circuit description
Circuit Diagram (Supply part)
Circuit Diagram (Control part)
Component Layout
Source Selector
Circuit diagram (Volume part)
Component Layout
Component Layout
Circuit Diagram (LF Selector)
CD Unit
Circuit Diagram
Component Layout
Alignment instructions
Service Testprogramme
Recorder Part
Circuit Diagram (Digital part)
Component Layout
Adjustment table
Circuit Diagram (Analog part)
Component Layout
Published by Consumer Electronics Printed in The Netherlands °Copyright reserved Subject to modification
45 - 46
47 - 48
50 - 52
53 - 55
CD Midi System FW2017
Tuner
Adjustment table
Component Layout
Circuit Diagram
Dismantling of Set
Exploded views
Front part
Tape Decks
Cabinet
CD Unit
Mechanical partslists
Front part
Cabinet
CD Unit
Electrical partslists
CD Unit
Front Panel
Recorder Part
Source Selector
Tuner
Power Board
20/21/22/25/30
ce
4
1
WOT
DIGITAL AUDIO
page
56
57 - 58
59 - 61
62 - 63
65 - 66
69 - 70
72
71
73 - 74
75-77
78 - 80
81 - 84
85 - 86
87 - 89
CLASS 1
LASER PRODUCT
3122 110 6420
4822 725 23707
PHILIDS
PHILIPS
CS 57 052

Specification
General: CD part:
Mains voltage : 220V / 50Hz for /20, /22, /28 Frequency response : 20-20.000 Hz +2 dB)
: 240V / 50Hz for /25, /30 Output level : 2V23dB
230V / 50Hz for /21 Signal /noise ratio : 290 dB
120V / 60Hz for /37 Distortion > $1% at 1 kHz
Channel difference : $2 dB at1 kHz
Power
consumption
<
150W
at
maximum
output
power
Channel
crosstalk
:
50
dB
max.
< 15W in stand by De emphasis : Qor 15/50 us switched automatically
by subcode on the disc
Tuner: Ee
Tuning
range
87,5
-
108
MHz
522
-
1611
kHz
(not
for
/37)
148
-
284
kHz
530 - 1700 kHz (only for /37)
Aerial input 75 Q (not for /17) Frame aerial Frame aerial
300 & (only for /17)
4 uV (2 wV typ.) 3 mV/m (1,5 mV/m typ.) 6 mV/m (not guaranteed above 250 kHz)
[ee eas re
Amplifier:
Output
power
:
2x20Wat8Q
0D=0,9%
(from
50
Hz
to
20
kHz)
+
1x
21W
at
42
D=0,9%
(from
30
Hz
to
120
Hz)
Music
power
:
2x
33Wat
8a +
1x
50Wat
4a
Headphone : 6,3mm stereo jack 1,4V into 322 D<1%
Power stage protection : AC, DC and Shortcircuit
Frequency
response
:
Bass
35
Hz
-
150
Hz
+
left
and
right
channel
250
Hz
-
20
kHz
(-3dB)
Tone
control
:
Bass
from
+10
dBto-10dB
+
2dB
at
100
Hz
: Treble from +10 dB to -10dB + 2dB at 12 kHz
DBB at 80 Hz : +10dB at -40dB
Input sensitivity : PHONO 5,5 mV
> AUX. 300 mV
Output voltage : LINE 400 mV
Recorder part:
Tape speed : 4,76 cm/s +2% in Normal Speed
: 8,55 cm/s +12% in High Speed
Wow & Flutter > ©$0,3%
Winding speed : $125 for C60 cassette
Noise reduction system : Dolby B (Noise Reduction factor: 7 dB typ.)
Erase / Bias system > AC 80 kHz
RiF-shift : service solution on request
Distortion at 250 nWb/m : <3%
Channel difference atPB : <3dB
Channel difference overall : <3dB
Channel separation >: $ 20 dB at 1 kHz
Track separation : $50 dB at 1 kHz
Frequency response 5.8”
” typical value 2) at 250 nWb/m
CS 57 053 2
1

GENERAL
CHIP
COMPONENT
SOLDER SOLDER
_— COPPER TRACK
P.C.B.
SERVICE PACKAGE
WARNING
All ICs and many other semi-conductors are
susceptible to electrostatic discharges (ESD).
Careless handling during repair can reduce life
drastically.
When repairing, make sure that you are
connected with the same potential as the mass
of the set via a wrist wrap with resistance.
Keep components and tools also at this
potential.
CF) ATTENTION
Tous les IC et beaucoup d’autres
semi-conducteurs sont sensibies aux
décharges statiques (ESD).
Leur tongévité pourrait étre considérablement
écourtée par le fait qu'aucune précaution n'est
prise a leur manipulation.
Lors de réparations, s'assurer de bien étre relié
au méme potentiel que la masse de |'appareil et
enfiler !e bracelet serti d'une résistance de
sécurité.
Veiller a ce que les composants ainsi que les
outils que |'on utilise soient également a ce
potentiel.
OISMOUNTING
VACUUM PISTON
SOLDERING 4822 395 10082
e.g. WELLER
SOLDER TIP PT-H7
SOLDERING
IRON
SOLDER WICK
4822 321 40042
e.g. A PAIR OF TWEEZERS
+
B
HEATING
4
HEATING
x
SOLDERING IRON
SOLDER WICK CLEANING
PRECAUTIONS
SOLDERING
SOLDERING
IRON
HIP
Cc
COMPONENT
(0) WARNUNG
Alle ICs und viele andere Haibleiter sind
empfindlich gegen elektrostatische Entiadungen
(ESD).
Unsorgfaltige Behandiung bei der Reparatur
kann die Lebensdauer drastisch vermindern.
Sorgen sie dafiir, dass Sie im Reparaturfail
Uber ein Pulsarmband mit Widerstand mit dem
Massepotential des Gerdtes verbunden sind.
haiten Sie Bauteile und Hilfsmittel ebenfalls auf
diesem Potential.
<>)
MOUNTING
e.g. A PAIR OF TWEEZERS
iV/p
SOLDER
@0.5-08mm
SOLDERING
PRESSURE
+
SOLDER
@0.5-08mm
SOLOERING TIME
<3 sec/side
PRESSURE / SOLDERING
+
EXAMPLES
i, ee.
SOLDERING
27 O12C12
CNL) WAARSCHUWING
Alte IC's en vele andere halfgeleiders zijn
gevoelig voor electrostatische ontladingen
(ESD).
Onzorgvuidig behandeien tijdens reparatie kan
de levensduur drastisch doen varminderen.
Zorg ervoor dat u tijdens repaatie via een
polsband met weerstand verboncien bent met
hetzeifde potentiaal als de massa van het
apparaat.
Houd componenten en hulpmiddelen ook op
ditzeifde potentiaal.
C1) awerrimento
Tutti IC e parecchi semi-conduteri sono
sensibili alle scariche statiche (ESD).
La loro longevita potrebbe essere fortemente
ridatta in caso di non osservaiiome della pits
grande cauzione alla loro maripolazione.
Durante le riparazioni occorre quindi essere
collegato allo stesso potenziakb che quello della
massa dell’apparecchio tramit um braccialetto
a resistenza.
Assicurarsi che i componenti ¢ ariche gli utensili
con quali si lavora siano ancht a questo
potenziale.
Safety regulations require that the set be restored to its original
condition and that parts which are identical with those specified be
used.
e
Les normes de sécurité exigent que l'appareil soit remis a |’état d'origine
et que soient utilisées les pieces de rechange identiques a celles
spécifiées.
<>)
Le norme di sicurezza esigono che |’apparecchio venga rimesso nelle
condizioni originali e che siano utilizzati pezzi di ricambiago identici a
quelli specificati.
GE) Varning!
Veiligneidsbepalingen vereisen, dat het apparaat in zijnoorspronkelijke
toestand wordt teruggebracht en dat onderdeien, identik aan de
gespecificeerde worden toegepast.
@
Bei jeder Reparatur sind die geltenden Sicherheitsvorsmré ften zu
beachten. Der Originalzustand des Gerats darf nicht vean dert werden
fur Reparaturen sind Original-Ersatzteile zu verwenden,
(eS) Varo!
Avattaessa ja suojalukitus ohitettaessa olet aittiina nakynaattomaille
lasersateilylie. Ala katso sateeseen.
Osynlig taserstraining nar denna del ar 6ppnad och sparren ar urkopplad.
Betrakta oj stralen.
CS 57 054

Connection & Controls
bh
CS §7 055

3.5
3.6
CONTROLS, Fig. 1
1.1 Control panel of DECK 1 (Switch 4822 276 13066)
EJECT: to open the cassette compartment.
WIND: fast winding in the direction indicated.
PLAY: to start playback in the direction indicated.
PAUSE: to pause during recording/playback.
STOP: to stop recording/playback.
1.2 Control panel of DECK 2 (Switch 4822 276 13066)
WIND: fast winding in the direction indicated.
PLAY: to start playback.
PAUSE: to pause during play.
EJECT: to open the cassette compartment.
STOP: to stop playback.
1.3 Control panel of the CD player (Switch 4822 276 13066)
SKIP: to select the required track.
PLAY/PAUSE: to start playback/pause during play.
STOP: to stop during play.
SHUFFLE: for playing ail tracks in a random order.
OPEN/CLOSE: to open/close the CD tray.
CONTROLS, Fig. 2
2.1 ON/STAND BY button (Switch 4822 276 13066)
To switch on and off (stand by).
2.2 TAPE DECKS - TUNER - COMPACT DISC - TV/AUX buttons
(Switch 4822 276 13066)
To switch on and/or select the sound source.
2.3 Control panei of Tuner and Cassette Deck
(Gwitch 4822 276 13066)
RECORDING: press (for at least 1 second) to start recording.
DIRECTION: to select the tape direction (deck 1).
MODE: to select continuous playback or autoplay function.
PRESET: to select stored preset stations.
SENSOR: infrared receiver for the remote control unit.
CD SYNCHRO: for synchronous starting when dubbing a CD to a
cassette in deck 1.
A.R.C.S. (Auto Rewind CD Synchro): for first fast reverse and then
synchronous starting when dubbing a CD to a cassette in deck 1.
24 VOLUME (Potmeter 4822 102 10441, Led 4822 130 81678)
Volume control with indicator (flashes when the remote control unit
is used and is lit when the unit is on or in stand by mode).
CONTROLS, Fig. 3
3.1 TIMER control panel (Switch 4822 276 13066)
3.4 Cassette deck function buttons (Switch 4822 276 13066)
H.S.D. (High Speed Dubbing): to dub at high speed.
DUBBING: to dub at normal speed.
CHROME: selector button for type of tape.
DOLBY NR button: to switch the Dolby NR (Noise Reduction)
system on and off.
3.5 Programming buttons for Tuner and CD (Switch 4822 276 13066)
CLEAR: in TUNER mode: to erase the indicated preset station. In
CD mode: to erase programmed CD tracks from the memory.
PROG.: to store preset stations and CD tracks in the memory.
3.6 CD control buttons for special functions (Gwitch 4822 276 13066)
REPEAT: to repeat all tracks or a program.
REVIEW: to check a program.
INTROSCAN: to play the start of all tracks.
3.7 Sound controls (Potmeter 4822 101 21169)
BASS and TREBLE: tone colour controls to adjust bass and treble.
BALANCE: balance control, to correct differences between the left
and right-hand channel.
3.8 DSP buttons (Switch 4822 276 13066)
With the Digital Sound Processor, you can select special sound
effects. You can choose from PRESENCE, HALL, STADIUM, LIVE
and CONCERT.
Press CANCEL DSP to switch off the Digital Sound Processor.
3.9 DBB button (Switch 4822 276 13066)
To emphasize bass tones.
CONNECTIONS, Fig. 4
4.1 Aerial connections
AM (4822 287 40668): for the frame aerial supplied for long wave
and medium wave (LW/MW). Aim the aerial for optimum reception.
FM 75 Q (4822 267 31128) for FM aerial. You can connect the
auxiliary aerial supplied to this. The use of an FM outdoor aerial
or cable aerial is recommended for good FM stereo reception.
4.2 Audio sockets (Chinch socket 4822 267 20373)
AUX: input for connecting a record player with a magneto-dynamic
cartridge, or for a separate recorder (only for playback), a separate
amplifier etc.
if a record player is connected, put button 4.3 (4822 276 13169) in
the MD position before switching on the unit, to avoid noises. If
you do not connect a record player, always put button 4.3 in the
AUX position.
TV: input for TV sound or a video recorder.
AUDIO: output for connecting a separate recorcler (only for
recording), or a separate amplifier.
TIMER: to set the start and stop time when using the timer
function. For example, to make a recording when you are absent.
TIME: to set the time. Then press SET - or + and finally TIME
again.
ALARM: to set the alarm time. Then press SET - or + and finally
ALARM again.
SET - and +: to set the time and alarm time.
CANCEL: 12 or 24-hour setting (after pressing TIME): to switch off
4.3 MD/AUX switch (4822 276 13169)
Set this switch to the MD position when connecting a record
player with a magneto-dynamic cartridge to the AUX input sockets.
If you do not connect a record player, always put button 4.3 in the
AUX position.
Always switch the unit to stand by, before operating the MD/AUX
the timer and sleep function.
button 4.3, to avoid undesired noises.
3.2 PHONES (Socket 4822 265 20534)
Socket for headphones (impedance 32 - 1,000 ohms). When
headphones are used, the loudspeakers are switched off.
4.4 VOLTAGE SELECTOR (4822 272 10269 not on all versions)
ff your unit has a voltage selector, check that it is set to the local
mains voltage.
3.3 TUNER control panel (Switch 4822 276 13066)
AUTO SCAN: to scan stored preset stations. 4.5 MAINS (4822 265 20291)
AUTO
PROGRAM:
to
program
preset
stations
automatically.
Socket
for
the
mains
lead.
BAND:
wavelength
selector
button.
:
TUNING:
tuning
buttons.
46
Loudspeaker
connections
SPEAKERS 8 Q : for the SATELITE speakers.
MONO: to reduce noise when receiving weak stereo transmitters.
? par BASS 4 Q: for the BARITONE bass speaker.
5 6 CS 57 056

WIRING DIAGRAM
PR-DECK _ REV,OECK
it 0 i 1
BROWN
GREY
GREY
8002
BLUE
| oeAnce |
ORANGE
ARINSTRANSFORNER
1010
BROW
BROWN
ALTE B260(FOR/17 ONLY?
RED
ALL PCBS SHOKN FROM THE COMPONENT SIDE
@—— SOLDER POINT. HANDSOLOERED
CS 57 057
VERSION
B
SLACK
3009
8015
PCBL
TUNER HERA C3
1001
CO-DECK
HERIPHONE

POWER BOARD
The
output
stage
is
switched
on
via
the
voltages
+STBY
and
-STBY.
These
voltages
are
derived
from
the
voltages
+VCC1
and
-VCC1,
respectively,
and
can
be
switched
off
via
the
astable
monoflop
(TS7287,
7290).
This
astable
monoflop
has
the
task
of
switching
off
the
output
stage
in
the
event
of
a
fault
(short-circuit
or
DC
at
the
output).
if
a
brief
fault
occurs,
then
the
output
stage
will
be
switched
off
for
around
4-5
seconds
(charging
time
of
C2276
via
R3288).
In
the
case
of
prolonged
DC
voltage
at
the
output,
TS7287
will
operate
as
a
switch
(see
faults
+/-
DC
at
the
output)
and
switch
off
the
output
stage
for
the
duration
of
the
fault.
Without
fault
is
the
state
of
the
monoflop
whereby
TS7290
is
conducting
and
is
blocking
transistor
7287
via
R3291.
As
a
result,
the
collector
of
TS7287
is
HIGH
(approx.
+11V).
Via
R3286
the
base
of
TS7280
also
becomes
HIGH
and
switches
the
latter
through.
This
causes
TS7279
and
7282
to
block.
Transistors
7278
and
7283
are
conducting
and
switch
through
the
voltages
+STBY
and
-STBY
respectively.
Faults:
+DC at the output: Via D6287 a positive voltage arrives at the base of TS7287, causing the collector of TS7287
to become LOW. TS7280 blocks. Via the potential divider R3279/R3281 a voltage of approx.
1V presents itself at R3281. The result is that a voltage of approx. 0.7V lies on the base of
7S7279 and the emitter of TS7282 respectively. The transistors switch through and thus
block TS7278 and 7283. The voltages +STBY and -STBY are not switched through and the
output stage is not operative.
-DC
at
the
output:
Via
D6290
a
negative
voltage
arrives
at
the
base
of
TS7290,
causing
it
to
block.
At
the
collector of
TS7290
there
now
reside
around
+20V.
TS7287
is
switched
through via
R3291,
causing
the
collector
of TS7287
to
become
LOW.
TS7280
blocks and
switches
the
unit
to
standby.
+/-DC
pulse:
Normally,
there
are
around
3V
DC
at
C2276.
If
TS7287
is
now
brought
into
conductance
by
a
pulse
(+DC
across
D6287,
-DC across
D6290/TS7290),
then
the
end
of the
elco,
which
had
previously
been
charged
to
+11V,
is
suddenly
on earth. As
the
other
end
of
the
elco
was around
3V more
negative,
a
negative
voltage
now
lies
at
the
base
of TS7290
and
blocks
it.
Consequently,
around
+20V reside at
the
collector
of TS7290.
The
+voltage
arrives
at the
base
of
TS7287
via
the
potential
divider R38291/
R3274+3249
and
keeps
it
in
conductance.
Meanwhile
C2276
is
charged
via
R3288.
After
4-5 seconds
the
voltage
at
C2276
has risen
so
far
that
transistor
7290
is
switched
through
again
via
R3289,
causing
transistor
7287 to be
blocked again via
R3291.
Short-circult at the output:
The principle on which the circuit operates is explained only on the basis of the right-hand channel and is of
course also valid for the left-hand channel and the bass channel.
in normal operation, with every positive half
wave via the feedback the base of TS7308
becomes more positive than the emitter. The
transistor remains blocked. D6302 prevents
switching through during the negative haif wa-
ve.
If during the short-circuit at the output the si-
gnal being fed back falls away, in the case of
the positive half wave the emitter becomes
more positive than the base. TS7308 is con-
ducting. D6308 is for a positive pulse in the
conducting direction. Via R3274 this positive
pulse reaches the base of TS7287 and swit-
ches the latter through. The astable monoflop switches off the output stage, as described under fault +/-DC pulse,
for 4-5 seconds. Due to threshold voltages (7308, 6308, 7287), this short-circuit interruption will only operate from
around 1.4Veff at the output of IC7322.
7322
Feedback
Fig. 1
9 Gs)

Current
limitation:
If
the
emitter
current
through
TS7304
increases,
the
voltage
at
R3312
will
also
increase.
Via
the
potential
divider
R3316/3314
the
latter
also
reaches
the
Bcsssa
7316
base
of
TS7318.
Once
the
threshold
level
oo is reached, TS7318 switches through. |
BDTS638 Consequently, the base of TS7304 beco-
nee
mes
more
negative
than
the
emitter
and
blocks.
B8CS48B
33290
22arR
Fig. 2
Signal path:
The
circuit
shown
in
Fig.
3
corresponds
in
principle
with
the
circuit
in
the
manual,
but
components
which
are
not
|
absolutely
essential
to
its
basic
understanding
have
been
omitted.
The transistors 7310 and 7316 are to be
considered
as
switches
rather
than
am-
sce’
plifier
elements.
The
power
supply
is
switched on and off via the +STBY and
-STBY voltages respectively.
If
the
preamplifier
(IC7322)
is
modulated,
a
current
flows
across
its
load
resistor
(3340),
which
in
first
approximation
is
calculated
from:
Signai iin
4
SPEAKER
é u,*V,
ee eo tu
R,
aoT638
Vy=
voltage
amplification
of
1C7322
Ug=
voltage
between
pin
2
and
3
Ra=
R3340
3312
A186
This
current
must
be
supplied
from
the
-vecs
power
supply
and
causes
an
AC
voltage
drop
at
resistors
3324
and
3320
which
modulates
the
output-stage
transistors.
Fig.
3
Mute:
The
preamplifier
is
muted.
If
the
base
of
TS7320
is
HIGH,
it
switches
through
and
short-circuits
the
input
signal
of
the
preamplifier
(7322).
Muting
occurs
when:
a)
the
astable
monoflop
is
active
(to
avoid
plops
when
switching
off
the
output
stage).
b)
the
headphones
are
connected
(base
of
TS7284
goes
to
LOW
via
connector
1256.
TS7284
biocks.
The
collector
is
HIGH,
so
the
base
of
TS7320
is
also
HIGH.)
c)
During
the
various
switching
operations
(source
selector)
a
MUTE
signal
(LOW
active)
is
supplied
via
pin
8
of
1251,
so
that
the
base
of
TS7284
goes
to
LOW.
10 CS 57 058

SCHEDA DI ALIMENTAZIONE
Lo stadio di uscita viene attivato dalle tensioni +STBY e -STBY. Queste sono ottenute rispettivamente dalle
tensioni +VCC1 e -VCC1 e possono essere interrotte attraverso il Monoflop astabile (TS7287, 7290). Quest’ultimo
ha il compito di disattivare lo stadio di uscita in caso di guasto (cortocircuito o corrente continua in uscita).
Se la disfunzione é di breve durata, lo stadio di uscita viene disattivato per circa 4-5 secondi (Tempo di carica di
C2276 attraverso R3288). Se la corrente continua permane sull’uscita, il TS7287 funziona come un interruttore
(Vedere “Guasti, + /-CC in uscita") e disattiva lo stadio di uscita per tutta la durata del guasto.
Assenza di guasto @ la condizione del Monoflop astabile, e consente di azionare il TS7290 e disattivare il
transistor 7286 attraverso I’R3291. In tal mado, il collettore di TS7287 passa a livello alto (ca. +11V). Attraverso
R3286, passa a livello alto anche la base di TS7280, attivando quest’ultimo. Di conseguenza, TS7279 e 7282 si
bloccano. | transistor 7278 e 7283 diventano conduttori e inseriscono nel ciruito le tensioni +STBY e -STBY.
Guasti:
+CC in uscita:
-CC in uscita:
Impulso +/-CC:
e
Attraverso D6287 giunge una tensione positiva alla base di TS7287. In tal modo, il collettore
di TS7287 passa a livello basso. TS7280 si blocca. Attraverso il ripartitore di tensione
R3279/R3281 si ottiene in corrispondenza di R3281 una tensione di circa 1V. Di
conseguenza, sulla base di TS7279 o sull’emettitore del TS7282 @ presente una tensione
di circa 0,7V. | transistor si attivano e bloccano cos TS7278 e 7283. Le tensioni +STBY e -
STBY non entrano nel circuito e lo stadio di uscita non funziona.
Attraverso D6290 giunge una tensione negativa alla base di TS7290. In tal modo,
quest’ultimo si blocca. In corrispondenza del collettore di TS7290 sono presenti ora circa
+ 20V. TS7287 viene attivato attraverso {'R3291. In tal mado, il collettore di TS7287 passa
a livello basso. TS7280 si blocca e predispone la macchina in Stand-by.
Di norma, in corrispondenza di C2276 sono presenti circa 3Vcc. Se ora, attraverso un
impulso (+CC attraverso D6287, -CC attraverso D6290/TS7290) TS7287 diventa un
conduttore, |’uscita del condensatore elettrolitico, in cui erano prima presenti +11V, va
improwisamente a massa. Sull’altra uscita del consensatore elettrolitico erano presenti
circa -3V, ed era presente una tensione negativa sulla base del TS7290, tramite la quale
questo viene bloccato. In tat-modo, sono presenti circa +20V in corrispondenza del
collettore TS7290. Attraverso il ripartitore di tensione R3291 /R3274+3249, la tensione
positiva perviene alla base del TS7287 e la tiene sotto tensione. Nel frattempo, C2276 viene
caricato attraverso |’R3288. Dopo 4-5 secondi, la tensione in corrispondenza di C2276 é
salita a tal punto che, il transistor 7290 viene nuovamente riattivato attraverso I’R3289. Di
conseguenza, il transistor 7287 viene nuovamente bloccato attraverso |’R3291.
Cortocircuito in uscita:
La funzione principale del circuito é chiarita solo facendo riferimento al canale destro e, naturalmente, vale anche
per il canale sinistro e per quello dei bassl.
Feedback
In condizioni normali, a ogni semionda positiva,
la base del TS7308 diventa, attraverso la
retroazione (feedback), pil positiva dell’emetti-
tore. ll transistor rimane bloccato. D6302 impe-
disce I’attivazione durante la semionda negati-
3340
100R va.
Se ora, per un cortocircuito in uscita, il segnale
di reazione viene soppresso, !’emettitore di-
venta, in corrispondenza della semionda posi-
Sc tiva, pi positivo della base. TS7308 si attiva.
D6308 si trova nella posizione di passaggio per
un impulso positivo. Quest’ultimo raggiunge,
attraverso 1’R3274, la base del TS7287 e attiva
7322
3354
7308
BCS558B
Fig. 1
quest'’ultimo. |! Monoflop astabile disattiva lo stadio di uscita, come nel caso dell’errore per impulso + /-CC per
4-5 secondi. Sulla base delle tensioni di soglia (7308, 6308, 7287) questa interruzione per cortocircuito funziona
solo a partire da 1.4Veff in corrispondenza di 1C7322.
9@)
Limitatore di corrente:
B8CS58eB
7316
7318
BCS48B
3320
220R
Fig. 2
Percorso del segnale:
7304
BOT63B
Con l’aumentare della corrente dell’e-
Mettitore attraverso 1S7304, aumenta
anche la tensione presente su R3312.
Quest'ultima, raggiunge, attraverso il
ripartitore di tensione R3316 / 3314 la
base del 1S7318. Se si raggiunge il
Aiea valore di soglia, TS7318 viene attivato. In
tal modo, la base di TS7304 diventa pil
negativa dell’emettitore e si blocca.
ll circuito illustrato nella Fig.3 corrisponde in linea di massima a quello riportato nel manuale; tuttavia, alcuni
componenti, non necessari per una comprensione generale, sono stati tralasciati.
| transistor 7310 e 7316 non vanno con-
siderati come amplificatori bensi come
interruttori. Attraverso le tensioni +STBY e
-STBY l'alimentazione viene fornita/interrotta.
Se ora il preamplificatore (IC7322) viene
modulato, attraverso la sua _ resistenza
(8340) passa una corrente, che in prima
approssimazione viene calcolata con la
seguente formula:
Vy = Amplificazione di corrente di IC7322
Us = Tensione tra i Pin 2 e 3
Ra = R3340
Questa corrente deve essere fornita
dall’alimentatore e provoca in corrispon-
denza delle resistenze 3324 e 3320 una
caduta della tensione di commutazione, che
modula i transistor dello stadio di uscita.
*vcc1
+STBY
Feedback
Stgnal itn
oH
3354
peel
-STBY 4
-vcec1
Fig. 3
Esclusione: | preamplificatore viene commutato silenziosamente. Se la base di TS7320 @ a liviilo alto, essa
attiva quest’ultimo e interrompe il.segnale di ingresso del preamplificatore (7322). Viene silenziata
nei seguenti casi:
a) il Monoflop astabile @ attivo (Per evitare Plop alla disattivazione dello stadio di uscita).
b) Le cuffie sono inserite (la base del TS7284 viene portato a livello basso dal spina 1256.
TS7284 si blocca. II collettore é a livello alto e di conseguenza anche la base diTS$7320).
c) Durante i vari processi di commutazione (Source Selector) viene trasmesso un je@gnale MUTE
(attivo a livello basso) attraverso il Pin 8 del 1251. In tal modo la base del TS7284 passa a livello
basso.
10a)
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