Bang & Olufsen BEOGRAM 4002 User manual

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VeeL ESET
a
a
HS C471
QR OL,
B
YPE 5523-5526
EOGRAM
4002-4004

Bang & Olutsen
1
O-1
INTRODUCTION
This service manual comprises Beogram 4002, type 5513, which have been
constructed on the basis of type 5503.
In the diagrams the components are provided with an individual position
number and a co-ordinate designation, e.g. B3. This designation refers te
the placing on the PC boards which are provided with a printed division into
fields and with letters and figures along the edge of the PC board. Therefore
there are no drawings of the PC boards in the-service manual. The diagram
for the CD-4 demodulator shows only one of the stereo channels and the
co-ordinate designation for right channel is bracketed, e.g. B3 (C2).
The diagrams, which may be unfolded, are placed at the back of the manual
so that it is possible to cpen at the preceding pages at the same time.
. The service manual is complete and contains the paragraphs mentioned in
the below table of contents. Supplementary sheets will only be made in case
of essential changes.
CONTENTS ; SEC.
Technical data - Disassembly ............ ae eae e tana ene 1
Electrical description... 2.0.0.0 0002. c esc ec e eee nes wa eeees 2
Mechanical adjustments - Lubrication chart . ween ewer ace eters 3
Electrical adj justmen? setae d eee eee eee ete een eee 4
Fault-finding ............... See cece eer euseces Lene eeaae wee 8
Mechanical parts fist 0.0.0.0... eeepc eee eee cc cece eens 6
Diagram - Electrical parts list - Conditions of measurement ..... T
Service tips .. 0. cece a cate ee eeeeusaceecvnere 8

1-1 Bang & Oluisen
BEQGRAM 4002
TECHNICAL DATA ; Type Ne. $513
Sound system Stereo, matrix - a.
Output 2x 0.6m
Speeds ; 33-45 rpm.
Tonearm Fangential
Autaimatic racard-size Yes
Automatic pickup movement Yes :
Automalic speed selection- Yes
Wow and fiutier, DIN = 29.05% —_
Wow and flutter, WRMS. =< +0.028% ___
Rumble DIN unweighted > 4508
Rumble BIN weighted = 6508
Speed deviation <_ 0.02%
Speed control range > 6%
Diat for speed 2 pointers
Siyius pressure range Q-+t.d gram
Tangential tracking _ < .04"
Litt system Electronic
Anjishaling Parallel tracking, error angle
compensaled
Molor . Servo contoted OG
Drive system Bell
Turntable . 30 cm 1.3 kg
Dust cover Hingéd and detachable
Fower supply . 117 valts .
Frequency 5G - 60 Hz
Power consumption 20 watts
Dimensions Wx Hx DO 49x10 38cm
Weight it kg
Pickup MMC 6000
Styius Pramanik diamond
Radius of curvature {GD-4 quadro]
Frequency range 20-15,000H7 + 1.506 __
20 - 45,000 Hz (CD-4)
Channel separation 7000Hz " = 25dB
400 - 40.000 Hz > 20da
"Channel difference « 1.508
Infegrmodulation : = 1%
Recommended siyius pressure i gram _
Compliance 30x 10-Bem/dyn
Eifective tip mass 6,22 m9
Output m¥fomisec, 6.6 mid? kohms -
Subject te change without nctice
DISASSEMBLY

Bang
&
Olufsen
2-1
ELECTRICAL DESCRIPTION
Since
the
circuitry
of
the
Beogram
4002
-
6000
type
551x
is
basically
idetitical
with
that
of
the
type
550x,
the
electrical
description
will
give
chief
attention
to
those
circuits
which
are
fundamentally
different.
Record wiping
With
33
activated
in
the
STAND
BY
mode,
the
turntable
will
rotaie
but
the
slide
will
not
travel
in,
making
record
wiping
possible.
In the STAND BY mode, 1TRI is kept forward biased through LR9, 1R7
and 1R6, 1f33 is activated, the junction of 1R9 and LR? is connected to
chassis potential. ITR1 is reverse biased, the collector goes high: this level is
transmitted through 1D8 to the base of series transistor LIC] as forward
bias, with the result that voltage is available fram the power supply section.
The high level is likewise transmitted to the electronic switch through 1D10,
thus blocking the functions of the electronic switch and preventing slide
transport.
The turntable will rotate only as long as 33 is activated.
Tacho control
The
turntable
is
driven
by
atacho-controlled
DC
motor.
A
generator
in
the
motor
furnishes
an
AC
voltage
whose
frequency
is
dependent
on
the
motor
speed.
This
AC
vollage
is
fed
to
the
network
1CS
-
1R24
to
pin
l
of
LIC3,
The
AC
voltage
is
converted
to
a
square,
which
is
passed
on
to
a
Schmit
trigger.
The
frequency
of
the
square,
dependent
on
the
motor
speed,
controls
one
of

Bang & Olufsen
the output levels of the Schmitt trigger; the other output level is controlied
from
a
variable
time
constant
network
consisting
of
1C3
-
1R4-1R16-2R1
for 45r.p.m. and 103- }RI5-1R1? -2R2 for 33 r.p.m.,
Mi
olor Variabie
frequency \ i / tne constant
TEI AA
Qul schmilt lngger
LLL.
la schaitt trigger
The output signal of the Schmitt trigger (pin 6) is integrated across 1 R19 -
1C8 and fed to pin 5 which is a differential amplifier. The integrated signal
at
5
will
be
a
DC
voltage
which
varies
with
the
motor
speed.
This
DC
voltage
is fed via the differential amplifier to a power amplifier. Fhe power amplifier
is connected as a variable resistor to chassis potential. 1C10- 1C9-1R20
prayides negative feedback tor the power amplifier (see sketch), preventing
“overregulation™.
1D14 - 1149 - 1R21 provide a guarantee that the voltage across the motor
can only reach a certain value (sec sketch).
Amplit. cohen
Normal speed
Speed
mal
When starting up from motor stand-still, the power amplifier will receive
heavy drive to obtain very rapid speed increase. Approx. §.5¥ is present al
the anode of 1D 14 so if the voltage at pin 4 goes below 4.6V, then 1D49, a
3.3V Zener diode, will be forward biased, thus preventing the voltage across
the motor from exceeding approx. 4.4V so that the speed increase when
starting up will not be so heavy that the motor reaches twice its wanted
speed, since the motor regulating circuil 1s capable of taking hold at twice
that speed.
The motor regulating circuit is powered with 9V via the series transistor
LTR2, controlled by 1D13. 1D13 is a 9 Zener diode.
a ernad

Bang&Olufsen
|
2-3
Automatic
speed-change switch, 33 - 45
Motor contrat
We will assume as our starting point thai a 17 cm record is on the turntable.
When ON is activated and the slide begins travelling in, the conditions for
lowering the pickup arm are not present.
The collector of 1TR6 will be low. This low level is transmitted to the base of
ITR8 as reverse bias.
The collector of {TR8 and hence the base of 11C2 will float, as a result of
which 11C2 will be reverse biased and 1RL1 will be in the neutral position
(the 33-r.p.m. positioa).
When the slide passes the position giver mark for touch-down on 30 cm,
43C1 and hence 1TR1? are reverse biased, the collector of 1TR17 goes high,
which high level will attempt to charge 1C2! of the time constant network
1R46- 121, bui since the 30 cm position marker is very narrow, 1C21]
cannot obtain 2 full charge before 41C1, and consequently 1TR17 are
forward biased. Since a4 17 cm record is on the turntable, the conditions for.
lowering the pickup arm are not yet present, and the slide will continue to
travel in. The slide reaches the position marker for 25 cm lower - 17 cm
speed change, 41C1 and hence 1TRI7 are again reverse biased, this time far
a longer time than for 30 cm because the mark for 17 cm speed change is
broader than the mark for 30 cm lower,
The
high
level
at
1TR17
can
now
have
time
to
charge
1C21,
1IC2
is
forward
biased,
1RL!
operates,
and
the
speed
changes
to
45
r.p.m..
When the slide reaches the mark for 17 cm lower, and we have a 17¢m
record on the turntable, the conditions for lowering the pickup arm are
present.
The
collector
of
1TR6
goes
high,
which
high
level
is
transmitted
to
the
base
of iT
RS
as
forward
bias.
The collector of 1TR8 goes low, and 112 is now kept forward biased
through 1RLI, 1R11, 1R25 and ITR8.

Lo pha
Magnet cail circuit
Bang & Oluisen
The collector of 1TR& is connected via 1D32 to the "Motor control IN”
section of the electronic switch so that automatic speed change to 43 r.p.m.
can occur only while the slide is travelling in (high at the collector of
1TR12). A low level at the collector of ITR12 places the cathode of 1D32 on
chassis potential, and 1C?1 cannot be charged.
When switching manually from 33 te 45 r.p.m., 45 is activated, relay ]RL1
operates, aud 11C2 is forward biased through IRL1 and IRiL. 1f33 ts
activated, the bias for 11C2 is shorted to chassis through 1D12, LIC2 is
reverse biased, and LRLI releases.
1D12 prevents 1{C2 from being forward biased through 19.
IDH protects against induction peaks. .
When the requirements for lowering the pickup have been met, the collector
o ITR6 is high; this high tevel is transmitted via 1D22 to the LOWER
section of the electronic switch as a fixed level at the cathode of 1D35, When
the slide switch passes the position giver mark, the collector of 1TR17 as
mentioned before goes high; this high level is transmitted to the base of -
1TR? as forward bias. 1020 will charge throngh 1D23, 1TR7 and 1D21.
The charging current in 1C20 gives a negative voltage jump at the cathode of
1D22. This low pulse is fed to the electronic switch to activate its LOWER .
section. To ensure that.1C20 will not pick up a charge from the speed-change
switch through 1D21 and 1TR7, 1D50 shorts the base of 1TR17 to chassis
potential when the collector of ITR6 is low.
1219 and the time constant network 1R4i - 1C19 ensure that automatic
lowering will not occur when ihe detector arm reaches in above the bright
portion of the turntable (with ao record on ihe turntable).
Ifa low level is applied to the base of 1TR9, 1TR9 is reverse biased, the
collector is high and 11C4 reverse biased; ORLI will be in the neutral
position,
+304
If the base of ITR9 goes high, | TR9 is forward biased; the collector goes
low, and 11C4 is likewise forward biased and magnet coil ORE operates.
Parts of the collector current of 11C4 will charge 1C23 across 1R55 and
1R54. When 1C23 is charged to a level of approx. 0.7V, 1TR10 is forward
biased. The collector current in 1TR10 will impose a Joad on the drive to
ITR9, 1TR9 draws Jess current; this limits the current in 11C4, and hence
the magnet coil, from 4 amps at the memeni the magnet coil operates to
approx. 150 mA. When 1C23 has accumulated a charge, [R53 and (R55 are
connected to operate as base bias divider for 1T RIO in such a way that the
higher the collector voltage at 11C4, the higher the forward bias of ITR10,
1TR10 draws-more current, the base of 1TR9 is more heavily loaded, and
the collector current in 11C4 is limited as mentioned abeve. 1TR10
accordingly provides negative feedback.

Bang
&
Olufsen
|
2-5
DEMODULATOR
Forsicer-
ker
Pick-up
MMC BOU0
O
PM equa-|
lizing
eOO\EK 37%
me
latrix
| Rear
Veastre
sierea
Low pas
17K
Elektro-
nisk CD-4
switch |
Netdel
Eftekt
begrenser
Power supply
The
CD-4
demodulator
has
a
stabilised
power
supply
of
its
own
which
uses
the
power
supply
of
the
control
circuits
as
reference.
Pa
9 Say
Carrier detector
The
power
supply
series
transistor,
TR102,
is
forward
biased
by
TR1O1
and
TR1OO,
whose
base
receives
20
V
of
bias.
The
emitter
voltage
of
TR102
is
stabilised
by
TRIO3
and
D101.
30KHz
niveau
input
RH
BkHz at PL

Matrix |
Bang & Oluisen
The carrier detector serves the purpose of limiting the lock-in range of the
PLL if 30 kHz carrier drops out. Limiting foHows the curve shown, the slope
of the curve (level range) being adjusted with R43. R11 is used for selecting
the 30 kHz level at which regulation starts.
JOKHZ
The matrix serves the purpose of mixing the sum and difference signals in
such a manner that the front and rear channels appear separately.
The principle of the matrix is, in one case, ta add the two signals together to
produce the front signal and, in the other, to subtract them so as to obtain
the rear signai.
The difference signal is fed from the output of the ANRS circuit ta the base
of TRG. TR8 and TR9 operate as a differential amplifier. The two
transisiors have a common emitter resistor so that, if the current in TR
increases, the current in TR8 will decrease conmensurately and vice versa.
.. Since the base of TR8 is shorted to chassis potential, signal-wise, we conse-
quenily obtain at the collector of TR9 a signal that is in phase opposition to
the signal at the base of TR9 and, at the collector of TRS, a signal that is in
phase with the signal at the base of TRY. The signals are mixed across
resistors R81, R83, R82 and R84, resulting in the appearance of the F and R
signais-at C52 and C53, respectively. ,

Bang & Oluisen
Stiand
2b
The silent circuil is tc ensure that the outputs of the Beogram 6000 are silent
when the pickup arm is not lowered.
cS2heo 4 CSkyetng E9,
Electranic y
CQ-4 suit
When the pickup arm is lowered, approx. 17 V will be present at pin 1 of P8.
The charge picked up by C104 ensures that the channels are silent while the
pickup arm is being fowered. When the bias at the base of TR108 reaches
approx. +1.2 ¥, TR108 is forward biased. The collector of TR108 goes low,
TR107 is reverse biased, the emitter of TR107 goes low, and if a CD-4
record is being played, the low level at the emitter of TR107 will be irans-
mitted to the bases of TRS, TR15 and TR16, respectively; both the front
and rear channels will then be open.
If the pickup arm is raised, the voltage at pin 1 of P8 drops to0 V. TR108
is reverse biased, the collector goes high and TR10? is forward biased.
The emitter of TRi07 goes high; this high level is transmitted to the base of
TRIS and, via DIOS, to the bases of TR16 and TRS, TR15, TRt6 and TRS
ate forward biased so that the signal path in both front and rear channels as
well as the difference signal in the ANRS circuit are shorted to chassis
potential. 7
D106 and R123 ensure rapid discharge of C104 when the pickup arm begins
to rise.