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Service Manual A32
Issue 1.0
FMJ A32, P35 & P35/3
Amplifiers
ARCAM
Contents List
! Phono board L870
o Circuit description
o Component overlay
o Parts list
o Circuit diagrams
! Amplifier & PSU board L882
o Circuit description
o Component overlay
o Parts list
o Circuit diagrams
! Display board L928
o Component overlay
o Parts list
o Circuit diagrams
! Preamplifier board L937
o Circuit description
o Component overlay
o Parts list
o Circuit diagrams
! 3rd Channel Amplifier board L911
o Component overlay
o Parts list
o Circuit diagrams
! Transformer specifications
o L914TX
o L915TX
! General assembly
o A32 - Mechanical parts list
o P35 - Mechanical parts list
o P35/3 - Mechanical parts list
Phono
Board
L870
Contents
! Circuit description
! Component overlay
! Parts list
! Circuit diagrams
AV8 Phono Board
Circuit Description
Refer to circuit diagram L870 sheet 1
The phono board is a simple single stage RIAA amplifier
and consists of two channels of high gain amplification,
and the ability to switch between moving magnet (MM)
and moving coil (MC) settings.
PSU
The unit derives its + 15V regulated rails from the unit it is
fitted into with only local decoupling capacitors on board.
Interface
The unit connects to the host unit via a 8 way connector.
Amplification
The left channel has designators beginning with 100, and
the right with 200. For the purposes of this description the
left channel will be described, as the right channel is the
same in all respects.
The amplifier is a small signal class A voltage feedback
amplifier with switch able gain. The input consists of an
actively loaded differential pair of very low noise PNP
transistors (TR106, TR107). These transistors are very
specific and should only be replaced with identical parts
with the E grade high gain. TR100 and TR101 form a
current source for the pair, which sets the quiescent current
for the entire amplifier. The active load consists of TR110
and TR111, which forms part of the differential current
mirror with TR112, TR113 & TR114. This differential
stage also has an active load (TR102 & TR103) to keep
gain to a maximum.
Both of these differential stages are designed to have as
much gain as possible to enable the single stage design.
The RIAA response is achieved in the feedback network:
C101, C110, C111, C112, C119, C120 and R115, R112.
C115 is used to correct between MM and MC gains as the
amplifier is non-inverting.
SW100 switches between MM and MC. Two poles of the
switch change between the different loading required for
each type of the cartridge: R108 & C109 for MM and
added in parallel for MC R104 & C108. The other two
poles change the feedback resister value to alter the gain:
R105 for MM and added in parallel for MC R123.
The DC offset is controlled by a non-inverting servo built
around IC100. The amount of servo current is different for
each gain setting via R111 (MM) and R124 (MC) so that
the low frequency high pass point remains the same for
both settings. However the high pass point for the circuit
is set by C113. This gives a warp filter, stops DC start-up
thumps from upsetting DC coupled circuitry and an
approximation of the RIAA/IEC curve (-2dB @ 20Hz)
The output is class A buffered by a dual mirror follower
(TR104, TR105, TR108, TR109). The quiescent current is
set by D100 and R118 and R119.
Closed loop stability is achieved with C16, C117, giving
symmetrical slewing capability.
L870 Phono Board Parts List Issue 2.0
Designator Part Description
C1 2A410 CERD 100N 63V -20% +80% RA
C100 2N622 ELST 22U 63V
C101 2D210 PPRO 1N0 5% 63V RA
C102 2P710AS ELEC 100U 25V SILMIC
C103 2P710AS ELEC 100U 25V SILMIC
C104 2K410 PEST 100N 63V 10%
C105 2K410 PEST 100N 63V 10%
C106 2K410 PEST 100N 63V 10%
C107 2K410 PEST 100N 63V 10%
C108 2D147W PPRO W 470P 63V 5% RA
C109 2D110W PPRO W 100P 63V 5% RA
C110 2D247N PPRO 4N7 63V 5% RA
C111 2D310 PPRO 10N 63V 1% AXIAL
C112 2D310 PPRO 10N 63V 1% AXIAL
C113 2K510 CAP MKS2 1U0 16V 10%
C115 2D213N PPRO 1N3 63V 5% RA
C116 2D147W PPRO W 470P 63V 5% RA
C117 2D147W PPRO W 470P 63V 5% RA
C118 2U610 ELST NON POLAR 10UF 35V
C119 2D110N PPRO 100P 63V 5% RA
C120 2D210 PPRO 1N0 5% 63V RA
C200 2N622 ELST 22U 63V
C201 2D210 PPRO 1N0 5% 63V RA
C202 2P710AS ELEC 100U 25V SILMIC
C203 2P710AS ELEC 100U 25V SILMIC
C204 2K410 PEST 100N 63V 10%
C205 2K410 PEST 100N 63V 10%
C206 2K410 PEST 100N 63V 10%
C207 2K410 PEST 100N 63V 10%
C208 2D147W PPRO W 470P 63V 5% RA
C209 2D110W PPRO W 100P 63V 5% RA
C210 2D247N PPRO 4N7 63V 5% RA
C211 2D310 PPRO 10N 63V 1% AXIAL
C212 2D310 PPRO 10N 63V 1% AXIAL
C213 2K510 CAP MKS2 1U0 16V 10%
C215 2D213N PPRO 1N3 63V 5% RA
C216 2D147W PPRO W 470P 63V 5% RA
C217 2D147W PPRO W 470P 63V 5% RA
C218 2U610 ELST NON POLAR 10UF 35V
C219 2D110N PPRO 100P 63V 5% RA
C220 2D210 PPRO 1N0 5% 63V RA
D100 3A4148 SSDIODE 1N4148 75V
D101 3A4148 SSDIODE 1N4148 75V
D102 3A4148 SSDIODE 1N4148 75V
D200 3A4148 SSDIODE 1N4148 75V
D201 3A4148 SSDIODE 1N4148 75V
D202 3A4148 SSDIODE 1N4148 75V
IC100 5B071 IC FET OPAMP TL071
IC200 5B071 IC FET OPAMP TL071
PCB1 L870PB_2 PRINTED CIRCUIT BOARD
R100 1H133 RES MF W4 1% 330R
R101 1H110 RES MF W4 1% 100R
R102 1H110 RES MF W4 1% 100R
R104 1H110 RES MF W4 1% 100R
R105 1H110 RES MF W4 1% 100R
R106 1H110 RES MF W4 1% 100R
R108 1H347 RES MF W4 1% 47K
R109 1H312 RES MF W4 1% 12K
R110 1H312 RES MF W4 1% 12K
R111 1H356 RES MF W4 1% 56K
R112 1H410 RES MF W4 1% 100K
R113 1H410 RES MF W4 1% 100K
R114 1H410 RES MF W4 1% 100K
R115 1H315 RES MF W4 1% 15K
R116 1H522 RES MF W4 1% 2M2
L870 Phono Board Parts List Issue 2.0
Designator Part Description
R117 1H522 RES MF W4 1% 2M2
R118 1H022 RES MF W4 1% 22R
R119 1H022 RES MF W4 1% 22R
R120 1H022 RES MF W4 1% 22R
R121 1H022 RES MF W4 1% 22R
R122 1H339 RES MF W4 1% 39K
R123 1H010 RES MF W4 1% 10R
R124 1H256 RES MF W4 1% 5K6
R200 1H133 RES MF W4 1% 330R
R201 1H110 RES MF W4 1% 100R
R202 1H110 RES MF W4 1% 100R
R204 1H110 RES MF W4 1% 100R
R205 1H110 RES MF W4 1% 100R
R206 1H110 RES MF W4 1% 100R
R208 1H347 RES MF W4 1% 47K
R209 1H312 RES MF W4 1% 12K
R210 1H312 RES MF W4 1% 12K
R211 1H356 RES MF W4 1% 56K
R212 1H410 RES MF W4 1% 100K
R213 1H410 RES MF W4 1% 100K
R214 1H410 RES MF W4 1% 100K
R215 1H315 RES MF W4 1% 15K
R216 1H522 RES MF W4 1% 2M2
R217 1H522 RES MF W4 1% 2M2
R218 1H022 RES MF W4 1% 22R
R219 1H022 RES MF W4 1% 22R
R220 1H022 RES MF W4 1% 22R
R221 1H022 RES MF W4 1% 22R
R222 1H339 RES MF W4 1% 39K
R223 1H010 RES MF W4 1% 10R
R224 1H256 RES MF W4 1% 5K6
SK1 8D230 PHONO SKT 2-WAY HOR EMC GOLD
SK2 8K2408 8-WAY AMP CT CONN
SW100 A1013 SW PUSH 4PCO
TR100 4A556 TRANS LF SS P BC556B
TR101 4A556 TRANS LF SS P BC556B
TR102 4A556 TRANS LF SS P BC556B
TR103 4A556 TRANS LF SS P BC556B
TR104 4A556 TRANS LF SS P BC556B
TR105 4A556 TRANS LF SS P BC556B
TR106 4A1085 TRANS LF SS P 2SA1085
TR107 4A1085 TRANS LF SS P 2SA1085
TR108 4A546 TRANS LF SS N BC546B
TR109 4A546 TRANS LF SS N BC546B
TR110 4A546 TRANS LF SS N BC546B
TR111 4A546 TRANS LF SS N BC546B
TR112 4A546 TRANS LF SS N BC546B
TR113 4A546 TRANS LF SS N BC546B
TR114 4A546 TRANS LF SS N BC546B
TR200 4A556 TRANS LF SS P BC556B
TR201 4A556 TRANS LF SS P BC556B
TR202 4A556 TRANS LF SS P BC556B
TR203 4A556 TRANS LF SS P BC556B
TR204 4A556 TRANS LF SS P BC556B
TR205 4A556 TRANS LF SS P BC556B
TR206 4A1085 TRANS LF SS P 2SA1085
TR207 4A1085 TRANS LF SS P 2SA1085
TR208 4A546 TRANS LF SS N BC546B
TR209 4A546 TRANS LF SS N BC546B
TR210 4A546 TRANS LF SS N BC546B
TR211 4A546 TRANS LF SS N BC546B
TR212 4A546 TRANS LF SS N BC546B
TR213 4A546 TRANS LF SS N BC546B
TR214 4A546 TRANS LF SS N BC546B
1 2 3 4 5 6 7 8
D D
C C
LEFT CHANNEL
Q_1 L870C2_2.0.SCH +15V
SK1 Q_3
LEFT IN LEFT OUT
PHONO2HG SK2
1 Q_5 1
2
3
4
EMC 0V_SIG 5
C1 Q_2 RIGHT CHANNEL 6
100N CD L870C3 2.0.SCH 7
Q_4 Q_6 8
RIGHT N RIGHT OUT
0V_SIG AMPCT8
Q_7 -15V Q_8
0V_SIG 0V_HF
B B
PCB1 DRAWING TITLE
A EL1 A
PCB
A85 PHONO STAGE - TOP LEVEL
Update Box
Circuit Diagram
23425
UPDATE_BOX
L870PB_2
Notes
01_1070 JAG 17/4/01 updated pcb and scm 2
A & R Cambridge Ltd.
Pembroke Avenue 00_1051 JAG 22/3/01 PRODUCTION ISSUE 1
Denny Industrial Centre ECO No. INITIALS DATE DESCRIPTION OF CHANGE ISSUE
Waterbeach Drawn by:
Cambridge CB5 9PB Filename Date Printed
Sheet 1 of 3
G:\DATA\ECO\ECO AGENDA\01 1070 l870 A85 PHONO ISSUE2\L870 2.0.ddb - L870c1 2.0.PRJ 23-Apr-2001 JBR DRAWING NO. L870C1
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
+15V
Q_102
+
C102 C104
100U SILMIC
100N PE
C119
D 0V_HF 0V_SIG D
R100 R101 R102
330R MF 100R MF 100R MF
100P PP
C101
TR100
BC556B TR102
1N0 PP TR103
BC556B BC556B
C110
TR101
BC556B
+ C100 4N7 PP
22U EL C120
R109 1N0 PP
12K MF C112
TR108 TR109
10N PP AX BC546B BC546B
C111
R115
R110
12K MF 15K MF
10N PP AX
R118
LEFT IN R112 22R MF
100K MF D100
SW100B 1N4148 C106
C 4PCO 100N PE C113 C
C105
C115 100N PE R116 LEFT OUT
N3 PP
1U0 PE
6
5
4
2M2 MF
R119
TR106 TR107
7
IC100 22R MF R122
2SA1085 2SA1085 R117
3 C118 39K MF
R111 Q 101 6 2M2 MF
56K MF 2
TL071CD 10U NP
R124
4
SW100D 5K6 MF R113 0V_SIG
R108 4PCO 100K MF TR104 TR105
47K MF BC556B BC556B
R104 C109
10
11
100R MF C108 100P PPW 12
470P PPW R105 R123 R114
100R MF 10R MF 100K MF
C117
C116
0V_SIG 0V_SIG 470P PPW
470P PPW
TR112 TR113
BC546B BC546B
B B
TR110
BC546B TR111
BC546B
TR114
BC546B
D101 D102
1N4148 1N4148
R106
100R MF
R120 R121 + C107
22R MF 22R MF 0V_HF C103 0V_SIG 100N PE
100U SILMIC
Q_103 -15V
DRAWING TITLE
A A
A85 PHONO STAGE - LEFT CHANNEL
Circuit Diagram
23425 Notes
01_1070 JAG 17/4/01 updated pcb and scm 2
A & R Cambridge Ltd.
Pembroke Avenue 00_1051 JAG 22/3/01 PRODUCTION ISSUE 1
Denny Industrial Centre ECO No. INITIALS DATE DESCRIPTION OF CHANGE ISSUE
Waterbeach Drawn by:
Cambridge CB5 9PB Filename Date Printed
Sheet 2 of 3
1 2 3 4 5
G:\DATA\ECO\ECO AGENDA\01 1070 l870 A85 PHONO ISSUE2\L870 2.0.ddb 6L870C2 2.0.SCH 23-Apr-2001
- JBR 7 DRAWING NO. 8L870C2
1 2 3 4 5 6 7 8
+15V
Q_202
+
C202 C204
100U SILMIC
100N PE
C219
D 0V_HF 0V_SIG D
R200 R201 R202
330R MF 100P PP 100R MF 100R MF
C201
TR200
BC556B TR202
TR203
1N0 PP BC556B BC556B
C210
TR201
BC556B
+ C200 4N7 PP
22U EL C220
R209 1N0 PP
12K MF C212
TR208 TR209
10N PP AX BC546B BC546B
C211
R215
R210
12K MF 15K MF
10N PP AX
R218
RIGHT IN R212 22R MF
100K MF D200
SW100A 1N4148 C206
C 4PCO 100N PE C213 C
C205
C215 100N PE R216 RIGHT OUT
1N3 PP 1U0 PE
3
2
1
2M2 MF
R219
TR206 TR207
7
IC200 22R MF R222
2SA1085 2SA1085 R217
3 39K MF
R211 Q 201 6 2M2 MF
56K MF 2
TL071CD C218
SW100CR224 10U NP
4
4PCO 5K6 MF R213 0V_SIG
R208 100K MF TR204 TR205
47K MF BC556B BC556B
C208 C209
R204
7
8
100R MF 100P PPW 9
R205 R223 R214
470P PPW 100R MF 10R MF 100K MF
C217
0V_SIG 0V_SIG C216 470P PPW
470P PPW
TR212 TR213
BC546B BC546B
B B
TR210
BC546B TR211
BC546B
TR214
BC546B
D201 D202
1N4148 1N4148
R206
100R MF
R220 R221 + C207
22R MF 22R MF 0V_HF C203 0V_SIG 100N PE
100U SILMIC
Q_203 -15V
DRAWING TITLE
A A
A85 PHONO STAGE - RIGHT CHANNEL
Circuit Diagram
23425 Notes
01_1070 JAG 17/4/01 updated pcb and scm 2
A & R Cambridge Ltd.
Pembroke Avenue 00_1051 JAG 22/3/01 PRODUCTION ISSUE 1
Denny Industrial Centre ECO No. INITIALS DATE DESCRIPTION OF CHANGE ISSUE
Waterbeach Drawn by:
Cambridge CB5 9PB Filename Date Printed
Sheet 3 of 3
1 2 3 4 5
G:\DATA\ECO\ECO AGENDA\01 1070 l870 A85 PHONO ISSUE2\L870 2.0.ddb 6L870C3 2.0.SCH 23-Apr-2001
- JBR 7 DRAWING NO. 8L870C3
Amplifier + PSU
Board
L882
Contents
! Circuit description
! Component overlay
! Parts list
! Circuit diagrams
Amplifier & PSU Circuit Description rails will vary with mains input and load conditions. The
current is around 20mA per relay.
Refer to L882 circuit diagrams
Star point SP100 is the ground `mecca' for the entire
This is the printed circuit board that provides the power amplifier (comprising all three PCBs within the unit). All
supply and output stage amplifiers for the A32 integrated and of the separately named grounds are joined explicitly at
P35 power amplifiers. this point. Different named grounds are used to ensure that
no two `different' grounds share copper, which could
Its function is to: compromise the noise, distortion or crosstalk performance
! Drive the loudspeakers of the amplifier.
! Provide an (always on) auxiliary 5VDC supply for the
micro controller and display interface The loudspeaker output signals are passed to socket
! Receive logic signals from the micro controller to turn SK106 which connects to SK107 and onto the headphone
on the main amplifier supply relay (mains) and connect output via the attenuation resistors R103 thru R106.
either pair of speaker output sockets
! Send logic signals to the micro controller pertaining to The hierarchy containing the other sheets is self
the state of the amplifiers (short circuit protection, DC explanatory. Each of the port names shown on the top
offset protection, thermal protection) sheet connects to the port of the same name on the lower
! Receive and demodulate RC5 remote style control sheets.
codes via the rear panel jack and transmit them to the
micro controller L882 Circuit Sheet 2
! Send a 12V trigger output via the rear panel jack for
control of an auxiliary power amp when the unit is on This sheet contains the power supplies, the rear panel jack
! Receive a 12V trigger input from the rear jack (for use socket trigger circuits, the standby relay control and the
in the power amp only version) `interface'circuits between the output signals of the power
! Drive a pair of headphones via attenuating resistor amplifiers and the inputs expected by the micro processor.
networks The power amplifier is a symmetrical, class B,
bipolar junction transistor output, current-feedback The mains input enters the unit at SK203, with capacitors
design (of which more later) with DC-coupled signal C205 and C206 acting as conducted RF suppression. The
and feedback paths, featuring an active integrating earth connection is passed on to the chassis (for safety
voltage servo to control DC offsets. reasons the chassis metalwork remains connected to mains
power earth at all times). Switch SW200 is the voltage
It features `instantaneous' safe operating area protection in selector switch, allowing the unit to be operated in 230V
addition to sending a signal to the micro to turn off the output or 115V mains countries by switching the dual-primary
relays in the event of user or thermal overload. Since it is a mains transformers between series and parallel winding.
DC-coupled design, the unit senses DC at the output and Varistors VR200 and VR201 act to prevent over-voltage
triggers the micro to turn off the loudspeaker relays in the surges from damaging the unit. If the user selects 115V
event of excessive levels (possibly due to a faulty source operation and then connects the unit to a 230V supply, the
component or short circuit output transistor). varistors will go to a low impedance and blow the primary
fuses. Any very high voltage line transients will also be
The output stage uses Sanken specialised `audio amplifier' suppressed, helping to eliminate transformer isolation
power bipolar Darlington transistors which are optimised for breakdown.
use with this type of topology. Consequently the unit has
excellent measured performance in terms of noise, slew rate, Relay RLY200 switches the primary side of the mains
output impedance and distortion (harmonic and transformer, allowing the micro to control the on / off
intermodulated) and is essentially load invariant (to a first status of the amplifier. Its contacts are snubbed by
order the measured performance is independent of the load capacitors C207 and C208 (to eliminate switching spark
impedance). transients and prolong relay lifespan). The primary
windings of the toroidal mains transformer connect to
L882 Circuit Sheet 1 SK204.
The audio input to the amplifier is connected to SK102 PCB mounted transformer TX200 is powered all the time
(which connects to the output of the preamp PCB). This that mains is present on SK203, irrespective of the on / off
signal is passed on via SK104A which forms the preamp out status of the amplifier. This is to ensure that the micro
connection to the outside world. processor is always operational and can thus control the
mains switching for the main amplifier. Secondary fuse
SK104B provides the power amp input connection, with F202 limits the current in the event of a failure mode, as
switchSW100 selecting between pre / power and integrated the short circuit primary current of TX200 would be
modes. The unit is wired as a preamp / power amp insufficient to blow the mains fuses.
combination with the switch depressed, allowing the user to
insert a processor or other function (e.g. graphic EQ) between Diodes D200 thru D203, C227 and IC201 provide the
the output of the preamp and the input of the power amp. 5VDC supply which powers the micro and display PCB
With the switch in the `out' position the power amp input and the relay coils. C224 is to reduce diode noise being
socket is ignored and the input to the power amp is connected transmitted back through the leakage capacitance of
internally to the output of the preamp. PL100 and PL101 are TX200.
`handbag' links fitted to the power amp only version to
connect both pairs of phono sockets in parallel for daisy The mains transformer secondary winding is connected to
chaining (as there is no preamp output on a power amp). SK200. This is a centre tapped winding, and is used with
full bridge rectifier BR200 to produce the main positive
Relays RLY100 and RLY101 switch the two pairs of and negative supplies for the power amp. C209 and C210
loudspeaker output sockets and are controlled by the micro are the large reservoir capacitors, with C211 and C212
lines describes above. Transistors TR100 and TR101 operate acting as high frequency decouplers. The main power
in `constant current sink' mode which allow relay current to supply rails and ground are accessible on SK205 for future
be approximately constant although the main power supply module expansion.
The circuitry around SK201A and IC200 is to receive and the feedback resistors that sets the overall gain of the
demodulate remote control commands sent in via the rear amplifier.
panel jack socket. This is for multi-room applications. L200
and C200 form a parallel resonant circuit at approximately IC300B acts as an inverting integrator and its purpose is to
37kHz. The output from this bandpass filter is passed into remove DC from the loudspeaker output. Any positive DC
IC200A where it is `chopped' and fed to IC200B to provide offset will cause the output of IC300B to go negative, thus
the output signal. increasing the current in its negative supply pin and
pulling the output voltage back towards zero. R330 and
C317 set the time constant of this integrator (0.47 seconds)
SK201B is a 13VDC signal trigger output which is active so that audio frequency components are ignored and only
whenever the amplifier is powered up. R218 and DZ207 / DC and subsonic frequencies are removed.
C223 provide a reference voltage which is buffered by
TR200. TR201 and R217 act as a current limit and prevent The input to the amplifier is limited to