Arcam P1 Service Manual
P1 AmpliÞer
ARCAM
Bringing music & movies to life
Service
Manual
Issue 1.0
ARCAM
Bringing music & movies to life
!
Circuit description
!
Circuit diagrams
o
L929AY switch PCB
o L962AY amplifier main PCB
!
Transformers
o L929TX – 115/230VAC toroidal
o L927TX – 100VAC toroidal
o
L907TX – 100VAC frame
!
Exploded view diagram
Contents List
!
Mechanical & packing parts list
!
Circuit board silk screen & parts list
o L929AY switch PCB
o L962AY amplifier main PCB
Fmj P1 Amplifier circuit description
roduct description
P
The
P1 has been has been designed to
by A.Moore
provide unsurpassed sound quality, the main
design features are as follows.
Gain switchable between Arcam gain
o
and THX gain (29dB closed loop) a 0dB
signal equates to 100 watts into 8
ohms.
P
ower supply/Control description
The
mains input is applied via SKT1. Y
capacitors C1 and C2 and X capacitor, C5
provide filtering and EMC suppression R2
provides a discharge path for the capacitors.
SW1 allows the selection of the mains voltage
that the unit will operate from, the main standby
transformer TX1 and the main transformer TX2
have duel primary windings, these windings are
connected in parallel for 115v operation and in
series for 230v operation.
o Input switchable between unbalance
phono and balance XLR.
o The amp is capable of producing >180
watts of sinusoidal output into an 8
ohm load and greater than 300 watts
into a 3.2 ohm load (subject to thermal
dissipation limits).
o Relay coupled for silent on/off
operation.
o Opto-isolated fault and control lines to
the control PCB.
o DC coupled signal path with
integrating servo to remove residual
DC errors.
o Instantaneous safe operating area
protection.
o Exceptionally low harmonic and
intermodulatiion distortion.
o Flat frequency response.
o Fast and asymmetric slew rate.
High damping factor
o
o Unconditionally stable into loads of
upto +/- 90-degree phase.
TX1 is powered at all times when a mains
voltage is applied to the mains input socket the
secondary of this transformer is fused by via FS3
and rectified by diode bridge DBR1 and
regulated to 5V by low dropout regulator at
location REG2 to provide a constant +5v(D)
supply for the micro.
Please note
: the digital supply ground is
connected to the chassis ground via a 100-ohm
resistor.
Relay RLY1 provides a means of powering the
main transformer for normal operation (as
apposed to standby operation where only TX1 is
powered) this relay is under the control of the
Micro IC1 and SW3 on the control board the
relay contacts of RLY1 are suppressed by C3
and C4 these prevent sparking and increase the
relay life span.
The circuitry around TR10 functions as a mains
present detection circuit A.C is feed into this
circuit before the Bridge network at location
DBR1 when mains is present the circuit drives HI
via opto-coupler TR11.
Relay 2 is the speaker output control relay this is
used to prevent clicks and pops at power/power
down and to disconnect the speaker output
under a fault condition, this relay is controlled by
the Micro at location IC1 as the P1 has no
manual speaker switching capabilities the micro
will automatically initialise the speaker relay 3
seconds after power up, the control line SPKR1
on pin 5 of CON 4 switches high to switch the
relay ON via TR9.
The P1 has two trigger inputs these are
applied by SKT2 and are wire OR-ed by D5
and D6. The single trigger signal is clamped
to 4v7 by DZ1 and fed to the control card by
CON4. Applying a 12v trigger signal to
either (or both) trigger inputs on the SKT2
instructs the microcontroller to enable or
disable the power amplifier. The trigger will
be seen as a HI line on Pin 11 of CON 4.
The P1 also provides two 2 triggered
outputs. These are current limited 12v D.C
levels, which are used to provide trigger
signals to other units within the customer’s
installation. The 12v output is present when
transformer TX2 is live i.e. when the unit is
not in standby.
TX2 has a Low voltage secondary winding
that supplies the trigger outputs only via
bridge rectifier DBR4 this is fed into REG1
(7812) regulator, TR1 and TR2 offer a
60mA current limit for both trigger outputs
and the entire circuit stage is fused by FS6
(T315mA) in case of overload.
The P1 utilizes a fairly unique
amp
power supply configuration these
main power
include.
The VAS stage is supplied by higher voltage
rails than the following output driver stage, this
allows the driver stage to fully saturate the
output driver stage without the use of a boot
strap circuit. This supply is exceptionally quite
and is critical to the sound quality of the P1.
Amplifier Stage
The
XLR connector at CON100 allows
balanced inputs to be applied to the amplifier
and CON101 allows for the balanced signal to
be daisy chained to a second P1.
The signal from CON100 is driven into IC100
this is a Balanced to single ended converter it
supplies a signal-ended output from a single
XLR input. The IC derives it power supply rails
from the +/- 67v rails these are dropped to
+/- 15v by the TR100 and TR114.
The unbalanced inputs signal arrives at
SKT100; the selection between the two input
options is accomplished by SW100. The
selected signal is clamped +/- 5v3 by the series
Zeners at location DZ103 and DZ104 this is to
prevent damage to the input of op-amp IC200,
due to leaky source signal or electrostatic
discharges.
Fig 1. Power amp power supplies.
Power supply Powers
+/- 67v D.C VAS stage.
+/- 58v D.C Output driver stage.
The t
wo sets of supplies are driven from
their own secondary windings and bridge
rectifier circuits DBR5 and DBR6 Rectify
the +/- 58v rails these are smoothed by
20,000uf of capacitance per phase. DBR2
and DBR3 are supplying the +/- 70v rails
these are dropped to +/- 67 by the Network
of R5, R6, R7, R8 and TR3, TR4, TR5, TR6
this is not a regulated supply as the rails
need to track the +/- 58v rails under mains
power fluctuations.
Please note: The +/- 70v rails are
individually fused by 315mA(T) fuses at
locations FS4 and FS5.
SW101 allows for the selection of two gain
settings these are 28.3 for “THX” and 37.5 for
the Arcam setting. The roll off setting is
340Khz.
The main power amplifier circuit is a classic
current feed-back design and can be thought of
as a large current feed-back op-amp the
topology is a refined high power output variant
of the A90/P7 design.
Op-amp IC101 is configured as a non-inverting
amplifier with a gain of 2. It’s purpose is to
provide current outputs (via it’s own power
supply pins) and a current input via it’s output
pin, the Op-amp performs the voltage to
current conversion (I-V) and phase splitting
necessary to drive the voltage gain stage. The
current feed-back occurs because the output of
IC101 drives into a 44 ohm load formed by the
two 22 ohm resistors R142 and R143 down to
ground, the power
Cont///
supply pin currents are half wave-rectified
versions of the drive current of the amplifier.
This causes the voltage gain, which is buffered
and passed on to the outputs. The feedback
from pin 1 of IC101 acts to reduce the gain of the
amplifier; when this current is roughly equal to
the current required to drive the input signal into
44-ohm’s equilibrium is reached and the closed
loop gain is defined. The output stage provides
the vast majority of the current required to drive
the 44-ohm load. The op-amp only needs to
provide a very small error current to give the
required voltage magnification.
Transistors TR101 and TR116 are common base
amplifiers their purpose is to provide the +/- 15v
rails necessary to drive the op-amp whilst
allowing the power supply currents that are
drawn to pass through into the Wilson current
mirror stage, this is formed by PNP transistors
TR102, TR104 and TR122 the NPN mirror is
formed by TR115, TR117 and TR122.
TR103 combines the two current mirrors to
provide a very high-gain current to voltage
(transresistance) gain stage roughly 80dB at low
frequency C114 and C132 with R149, R150
combine to give a open-loop pole at roughly
10Khz and a corresponding open-loop zero
around 500Khz. This allows for good time
domain performance and clean square wave
reproduction with no sign of ringing or overshoot.
Diodes D100 and D101 act to limit the current
through TR115 and TR112, if the input current
exceeds 14mA the diodes conduct and the
transresistance stage becomes a constant
current source killing the open loop gain and
preventing damage to the transistors.
TR103 provides a 4.7v bias voltage to allow
the following pre-driver stage to operate in
Class A.
TR123 and TR125 form a Class A pre-driver
emitter follower stage to boost the current gain
and isolate the transresistance stage from the
output transistors. TR105 and TR118 act as a
30mA current limit and prevent the destruction
of TR123 and TR125 under a fault condition.
R109, R164, R110 and R165 loosely decouple
the emitters of TR123 and TR125 from the
output stage.
TR128, TR129 and TR126, TR127 are Sanken
SAP 15N and SAP 15P Bi-polar output drivers
RV100 is the Bias adjust preset D104 protect
the Output drivers from destruction if RV100
goes open circuit.
C144 to C147 provide local R.F stability and
prevent oscillation. D111 and D112 are catch
diodes to reduce the effects of back-EMF from
the loudspeaker coils/load.
R164, R183, C150 and L100 form the Zobel
network, these components ensure that the
amplifier sees a constant load of 4.7 ohms at
high at very high frequencies and improve
stability – reduce H.F noise. L100 and R183
decouple the load at high frequencies to
ensure amplifier stability into capacitive loads.
SAP 15NY SAP 15PY
IC101 forms a D.C intergrating servo. Its
purpose is to remove residual D.C errors due to
slight device mismatch and component
tolerances. It is configured as an inverting
intergrator with a time constant of <0.5 seconds.
Any D.C offset at the output of the amplifier will
cause the output if the op-amp to go negative
increasing the current in the negative supply pin
and thus pulling the output down to ground (and
SAP
vica versa). D108 protects the inverting input of
the op-amp under fault condition.
S-E 0.22 Ohm
Under output driver failure conditions the 0.22 internal
emitter resistor will usually go open, the resistor should be
measured between pins S and E.
Protection circuit block
The P
1 Power amplifier incorporates 4 modes of
protection these are as follows.
o Instantaneous VI current limiting.
D.C offset protection.
o
o Over-Temperature.
o Insulation failure.
VI current
The
limit circuit is built around TR106
and TR119 they sense the voltage across the
0.22-emitter resistors (hence emitter current) and
the collector emitter current or device power
dissipation exceeds a preset limit.
The circuit is designed to allow large unrestricted
currents into loads of 3 ohms and above but limit
the current into a short circuit or very low
impedance loads.
C141, C142 and R162, R163 form a 2.2ms time
constant, which will allow larger transients of
current delivery for a few milliseconds, to ensure
that the amplifier has a sufficiently large transient
capability to drive “difficult” loudspeaker loads.
TR106 senses positive current surges and
TR119 senses negative surges these intern
activate TR107 and switch the optocoupler
OPTO100A this fault notification is sent to the
microcontroller and the output relay is switched
off to protect the amplifier/loudspeaker coils.
D.C offset
The
protection is built around TR108
and TR109 a positive D.C offset will switch
TR108, a negative D.C offset will switch TR120
this will intern switch TR110 and TR109 on in
either case this causes the optocoupler at
location OPTO100B to transmit a fault line signal
to the micro.
RTH100 is low when the amplifier is cool
typically a few hundred ohms, in the event of a
thermal overload situation (Above 110 c)
RTH100 will go into a high impedance state
this will switch TR121 on and intern this will
switch TR111 on and cause OPTO 100C to
send a fault line flag to the micro.
The remaining protection stage is an
insulation breakdown detect circuit this is
essentially looking for a breakdown of the
insulating pad between the output devices and
the heatsinks thus +60v path to ground.
The protection is formed around bridge rectifier
package DBR100, this will route current
through the LED in optocoupler OPTO 100D in
the event that the DGND and AGND ground
planes move apart by more than 10v. When
the transistor in the Opto conducts the thyristor
formed by TR112 and TR132 is turned On.
Once the Thyristor conducts it pulls the
SHUTDOWN* signal low and turns TR8 (Sheet
2) off thus opening both Speaker relays and
the Power relay.
Please note
: The unit can only be reset once
the mains power supply to the unit has been
removed and the Amplifiers own power
supplies have been given sufficient time to
discharge +30 secs. The standby transformer
of course remains active.
TR130 asserts the microprocessor fault line
DCPROT so that the micro can indicate the
fault via the front panel mounted LED.
Fig 2 Fault line location and operational status.
Pl
ease note:
Con 4 is the connector between
the main board and the display board, use Pin
2 of Con 4 as a reference (DGND).
The Thermistor RTH100 provides
protection
and is connected to the positive
Thermal
supply rails adjacent to the collector leg of the
output driver at location TR125 this allow the
thermistor to sense the temperature of the output
device. The output impedance of
Fault line Location Status
D.C offset Con 4 Pin 9 LOW (0v)
V/I Prot Con 4 Pin 8 LOW (0v)
Thermal Con 4 Pin 7 LOW (0v)
Test Specification
Major component identification.
Fr
equency response
. 8-ohm load
Input set to 1v rms
20Hz – 20kHz = +/- 0.5 dB
Distortion
. THD+N 0dBR 4-ohm load.
.
Input set to 1v rms.
20Hz – 20Khz = <0.02%
aximum output
M
into an 8-ohm load.
Input level set to 1.34 rms 1Khz = 180 watts
di
stortion should be below 0.05%
THD+N
Bias setting notes
FMMT 497/597
BC849/BC859
1=Base
2=Emitter
3=Collector
TLO 72
The bias
of the P1 is set using an Audio
precision audio analysis package and we
calibrate the power stage for minimum THD the
bench set up procedure follows.
o
Set the input signal to 150mv rms,
frequency to 10kHz. Induce a 4-ohm load
at the speaker output.
o
Rotate preset RV100 clockwise and
observe that the THD falls. Continue to
rotate the preset until the THD falls to a
minimum level and just starts to clime
again.
o
Switch input signal off and allow the
amplifier the Quiesce +30secs
o
Measure the bias level at test point Con
103 (Bias read) and confirm the reading is
below the absolute max of 35mV.
SSM2143
74HC32N
ITEM1 1 Blank PCB P35/P1 FMJ Amp Microcontroller BoardL929PB
+5V_D
CON1
MOLEX
5229-NAPB
CON2
MOLEX
5229-NAPB
D2
1N4148
DO-35
C8
100UF
25V
YK
R1
10K
0W25
MF
R2
10K
0W25
MF
SP2 LED
SW1
SKHVPB000A
2
SP2 SW
IC2E
74HC32N
DIP-14
14
VCC
7
GND
TR1
BC556B
TO-92
R12
560R
0W25
MF
1
0V_D
LED1
5mm
GRN
LED 5mm
+5V_D
14
13
12
11
10
9
8
7
6
5
4
3
2
1
R22
R23
R24
10K
10K
0W25
MF
R10
10K
0W25
MF
10K
0W25
MF
R11
10K
0W25
MF
0V_D
0V_D
0V_D
0W25
MF
0V_D
+5V_D
14
13
12
11
10
9
8
7
6
5
4
3
2
1
R9
10K
0W25
MF
0V_D
+5V_D
C14
100UF
R19
25V
YK
470R
0W25
MF
R20
470R
0W25
MF
R21
470R
0W25
MF
0V_D
R17
10K
0W25
MF
R18
10K
0W25
MF
R25
10K
0W25
MF
R26
10K
0W25
MF
TR5
BC546B
TO-92
TR6
BC546B
TO-92
TR7
BC546B
TO-92
SPARE1
STANDBY
SPKR1 ON
SPKR2 ON
THERMPROT 1
VIPROT 1
DCPROT 1
AC PRESENT
TRIGGER
REMOTE
SPARE2
STANDBY
SPKR1 ON
SPKR2 ON
THERMPROT 2
VIPROT 2
DCPROT 2
AC PRESENT
TRIGGER
REMOTE
SPKR1 ON
SPKR2 ON
STANDBY
SP2 SW
SP1 SW
SP1 LED
SPKR2 ON
SPKR1 ON
STANDBY
PWR SW
REMOTE
TRIGGER
AC PRESENT
THERMPROT
LK1
0R0
0W25
MF
0V_D
LINK LK1 IS USED
TO CONFIGURE PCB
FOR USE IN P35 OR P1
FOR P35 - LEAVE LK1 INTACT
FOR P1 - CUT LINK
THERMPROT 1
THERMPROT 2
VIPROT 1
VIPROT 2
DCPROT 1
DCPROT 2
SPARE1
SPARE2
0V_D
IC2A
1
2
74HC32N
DIP-14
IC2B
4
5
74HC32N
DIP-14
IC2C
9
10
74HC32N
DIP-14
IC2D
12
13
74HC32N
DIP-14
LK2
0R0
0W25
MF
0V_D
3
6
8
11
IC1
HT48R30A-1
L019SW
DIP-28
1
PB5
2
PB4
3
PA3
4
PA2
5
PA1
6
PA0
7
PB3
8
PB2
9
PB1
10
PB0
11
VSS
12
(TMR)/INT
13
PC0
14
PC1
THERMPROT
VIPROT
DCPROT
SPARE
PB6
PB7
PA4
PA5
PA6
PA7
OSC2
OSC1
VDD
RES
PC5
PC4
PC3
PC2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
DCPROT
VIPROT
SP2 LED
PWR GRN
PWR RED
SPARE
+5V_D
C2
100N
50V
X7R
0V_D
DRAWING TITLE
C1
100N
50V
X7R
D1
1N4148
DO-35
C3
100N
50V
X7R
+5V_D
R16
100K
0W25
MF
C5
10UF
50V
YK
C4
100N
50V
X7R
X1
4 00MHz
SIL-3
3
C6
100UF
25V
YK
1
2
C7
100UF
25V
YK
R3
10K
0W25
MF
R4
10K
0W25
MF
SP1 LED
SW2
SKHVPB000A
1
2
SP1 SW
FIX1
Dia 3.5mm
1
0V_D
TR2
BC556B
TO-92
R13
560R
0W25
MF
LED2
5mm
GRN
LED 5mm
FIX2
Dia 3.5mm
C9
100N
50V
X7R
R5
10K
0W25
MF
R6
10K
0W25
MF
PWR RED
SW3
SKHVPB000A
1
2
PWR SW
FIX3
1
Dia 3.5mm
C10
100N
50V
X7R
TR4
BC556B
TO-92
3mm
BICOL
LED 3mm
RED GRN
FIX4
1
Dia 3 5mm
C11
100N
50V
X7R
R14
330R
0W25
MF
0V_D
1
R15
180R
0W25
MF
TR3
BC556B
TO-92
LED3
FIX5
Dia 3.5mm
C12
100N
50V
X7R
R7
10K
0W25
MF
R8
10K
0W25
MF
PWR GRN
1
C13
100N
50V
X7R
P35 / P1 Switch PCB
TOOL1 TOOL2
ARCAM
A & R Cambridge Ltd.
Pembroke Avenue
Waterbeach
Cambridge CB5 9PB
Filename:
Notes:
Contact Engineer:
L929CT_1.0.sch
KAL 8/05/03 Redrawn, LED1, 2 swapped, Connectors rewired, LK1, 2 added 1.003_E125
WAF 2/01/02 HOLTEK, Z1 UPDATED B.103_E001
JR 1/11/01 LEDS TO 5MM AND MAINS SWITCH B.0
ECO No. DESCRIPTION OF CHANGE
Contact Tel: (01223) 203243Kevin Lamb
INITIALS
Printed:
DATE
13-May-2003
1 1Sheet of
A3
DRAWING NO.
L929CT
ISSUE
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