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Arcam Alpha 9 Service Manual

Arcam alpha 9 integrated amplifier service manual
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Handbook - 13 pages
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ALPHA 9/9P SERVICE MANUAL
ALPHA 9/9P SERVICE MANUAL
ARCAM ALPHA 9/9P SERVICE MANUAL
Issue 1 Serial No. 001 - (Paul Newton July 96)
Circuit Description
Input/Output Selection
The Alpha 9 integrated amplifier has 6 line level
inputs and optional phono input selected by use of
the motorised 'listen' switch, SW201.
The use of the 'record' switch SW202 allows
recording of one source whilst listening to another.
The Processor/Tape 2 switch, SW207, allows tape
monitoring of a 3 head tape deck connected to the
Processor/Tape 2 sockets. It can also be used to
allow input signals to be routed to an external
surround decoder for processing before being
routed back to the Alpha 9.
Tone Control & Preamp Out/Power Amp In
The tone control stage on the Alpha 9 is based
around a dual op-amp Z2. The first half provides
a buffer stage for the tone controls and the second
one with its frequency dependent feedback is used
as the tone control itself.
The output of the tone control then passes through
the balance control RV201 and then onto the
power amp stages and the preamp out buffer
stage formed by Z203.
The tone controls and balance pot can be
bypassed by use of the 'direct' switch SW205.
The Alpha 9 can be driven from an external
preamplifier source by moving the internal switch
SW206 to disconnect the Alpha 9 preamp stages
from the power amp.
Power Amplifier
The signal from either the Alpha 9 input sockets or
an external preamp enters the power amp stage
via C12 and R35.
Q11, Q16 form a long, tailed pair driven by the
current source formed by Q18 and Q19.
Q6 is the Class A stage driving the quasi
complementary output stage of Q4, Q5, and
mosfet's Q1, 2.
The Alpha 9 and Alpha 9P utilize an auto bias
circuit to maintain the correct quiescent current
(IQ). The circuit works by monitoring the voltage
across the 0.22 ohm resistors R1, RA1 and
comparing it to a voltage derived from the - 44v rail
via R24. Both these voltage are fed into the inputs
of comparator Z3. If the voltage across the 0.22
ohm
resistors
increases
comparator goes high impedance and Q15 is
turned off. This causes capacitor C72 to discharge
and reduce the bias on the base of Q17 which
reduces the IQ. Conversely if the voltage across
the 0.22 ohm resistors is low then Q15 is turned on
more and C72 charges and increases the bias on
Q17 and so increases the IQ.
conditions a low frequency, variable mark/space
ratio, waveform can be seen on the collector of
transistor Q20 as the bias is being automatically
adjusted.
Z1 is a d.c. servo used to maintain a low d.c. offset
at the speaker outputs.
Power Supplies
The Alpha 9/9P is powered by a toroidal
transformer with 2 sets of secondary windings.
The main windings are used to provide +/-44V
D.C. after rectification and smoothing by diodes
D201-204 inc. reservoir capacitors C201, 202.
The second winding is rectified to provide an
unregulated supply voltage for the motor driver ics,
Z402 (for the volume control) & Z403 (for the listen
selector).This unregulated supply is also smoothed
and regulated with a simple stabilizer circuit (zener
diode D402 and associated components) to
provide a stable voltage for the micro controller
Z401.
Protection/ Mute circuit
The protection and mute functions are carried out
by Z501. This performs turn on delay, d.c. offset
detection and thermal cutout. It also displays the
status of the amplifier with the use of a bicolour
LED - 'Green' for ready and 'Amber' for when the
speakers are disconnected internally because of a
fault condition or on initial power up whilst the 5
second switch on delay mute is operating.
If the unit suffers a current overload the protection
circuit may latch and the unit will not reset until it
has been switched off and on again. If the
protection is activated by a thermal problem the
unit will begin to operate again when it has cooled
down.
The thermal cut out operating point is set by the
thermistor TH501, mounted close to the output
device heatsinks.
Disc Stage (optional)
the
output
of
the
Under signal

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  Summary of Contents for Arcam Alpha 9

  • Page 1 Tone Control & Preamp Out/Power Amp In transformer with 2 sets of secondary windings. The tone control stage on the Alpha 9 is based The main windings are used to provide +/-44V around a dual op-amp Z2. The first half provides D.C.
  • Page 2 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL The optional phono stage board available for the Disassembly For Servicing Alpha provides amplification RIAA equalization for both moving coil (MC) and moving Remove the top cover and front panel. magnet (MM) cartridges.
  • Page 3 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL Alpha 9 Integrated Amplifier Parts List Alpha 9 Integrated Amplifier Parts List Ref. No. Description Part No. Ref. No. Description Part No. ELST 100U 25V 2N710 C106 PSTY 56P 160V ENCAP 1PF%...
  • Page 4 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL C402N CERD 10N 63V 20% RA 2A310 D104 ZENER 10V 400MW 3C11004 C403N ELST 1M0 25V 2N810 D106 ZENER 22V 400MW 3C22004 C404 CERD 10N 63V 20% RA 2A310 D201 RECTIFIER MUR420 4A 220V...
  • Page 5 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL LK401N JUMPER 3 WAY x 125mm L815CA Q109 TRANS LF SS N BC546B 4A546 LK501N LINK BANDOL PREFORM 10mm 1X010A Q110 TRANS LF SS P BC557B 4A557 LK601 JUMPER 3 WAY x 125mm...
  • Page 6 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL RES MF W4 2K7 1% 1H227 R54N RES MF W4 1K8 1% 1H218 RES MF W4 2K7 1% 1H227 R55N RES MF W4 1K0 1% 1H210 RES MF W4 4K7 1% 1H247...
  • Page 7 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL R112 RES MF FU W3 220R 5% NFR25 1G122 R148N RES MF W4 4K7 1% 1H247 R113 RES MF FU W3 470R 5% NFR25 1G147 R149N RES MF W4 1K8 1% 1H218...
  • Page 8 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL R207 RES MF FU W3 10R 5% NFR25 1G010 R527 RES MF W4 10R 1% 1H010 R401N RES MF FU W3 10R 5% NFR25 1G010 R601N RES MF W4 22R 1% 1H022...
  • Page 9 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL Alpha 9 Amplifier Non PCB Parts, Metalwork etc. SW202N SW ROTARY 6W 4 POLE A1210 SW205N SW PUSH 2PCO A1008 Part No. Description SW206N 2PC SLIDER SW MSS2200 A1401 B3002 AA BATTERY FOR REMOTE CONTROL...
  • Page 10 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL Alpha 9P Power Amplifier Parts List Alpha 9P Power Amplifier Parts List Ref. No. Description Part No. Ref. No. Description Part No. ELST 100U 25V 2N710 C172 ELST 100U 25V 2N710 PEST 47N 63V 5%...
  • Page 11 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL D104 ZENER 10V 400MW 3C11004 TRANS POWER MOSFET IRPF240 4K240 D106 ZENER 22V 400MW 3C22004 TRANS LF SS P 2SA1085 4A1085 D201 RECTIFIER MUR420 4A 220V 3B420 TRANS LF SS N 2SC2547...
  • Page 12 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL Q116 TRANS LF SS N BC547B 4A547 RES MF FU W3 10R 5% NFR25 1G010 Q117 TRANS LF SS N BC547B 4A547 RES MF FU W3 470R 5% NFR25 1G147 Q118 TRANS LF SS N BC547B...
  • Page 13 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL R106 RES MF FU W3 100R 5% NFR25 1G110 R159 RES MF W4 27K 1% 1H327 R107 RES MF W4 470R 1% 1H147 R160 RES MF W4 1K0 1% 1H210 R108 RES MF FU W3 100R 5% NFR25...
  • Page 14 ALPHA 9/9P SERVICE MANUAL ALPHA 9/9P SERVICE MANUAL R511 RES MF W4 18K 1% 1H318 COPPER RIVET HP007 R512 RES MF W4 18K 1% 1H318 COPPER RIVET HP007 R513 RES MF W4 33K 1% 1H333 IC AUDIO NE5534N 5A5534 R514...
  • Page 15 1N0 CD SW202NF A1210 Case SW202NG DRAWING TITLE 23425 A1210 SW202NH ALPHA 9 INPUT SELECTION THIS CAPACITOR TO BE BESIDE SK302 A & R Cambridge Ltd. A1210 Circuit Diagram Pembroke Avenue MAY96 ORIGINAL ISSUE L827C101 ALL COMPONENT DESIGNATORS ENDING IN 'N' ARE NOT ON ALPHA 9P...
  • Page 16 L815CA DRAWING TITLE SW402NB 23425 A1402 ALPHA 9 REMOTE CONTROL ALL COMPONENT DESIGNATORS ENDING IN 'N' ARE NOT ON ALPHA 9P A & R Cambridge Ltd. Circuit Diagram Pembroke Avenue ALL COMPONENT DESIGNATORS ENDING IN 'P' ARE ONLY ON ALPHA 9P...
  • Page 17 10MM LINK R161 R153 33K MF 2K2 MF PWRR +15v DRAWING TITLE 23425 INT/EXT Power Amp Source ALPHA 9 TONE CONTROL Z2NC Z102NC A & R Cambridge Ltd. Z203NC Circuit Diagram TL072 Pembroke Avenue JRC4560 JRC4560 ALL COMPONENT DESIGNATORS ENDING IN 'N' ARE NOT ON ALPHA 9P...
  • Page 18 +44V BOOTL ATE_PAD +15V 1N4003F R26 2K7 MF 100U EL 15N PE 470R FU 470R FU SRVOL 5K6 MF 100K MF BC557B NE5534 1K0 MF ATE_PAD 2SA1085 100R FU DC Servo IRFP240 2SC2547 AMPIL 100R MF 120K MF 2K7 MF SPKL ATE_PAD 47K MF...
  • Page 19 TARGET Drilling Update Box Detail HP007 DRILL_DETAIL SK503 SCRN ALL COMPONENT DESIGNATORS ENDING IN 'N' ARE NOT ON ALPHA 9P TOOLING4.1 TOOLING4.1 PAD200/1.4 IEC3 ALL COMPONENT DESIGNATORS ENDING IN 'P' ARE ONLY ON ALPHA 9P TARGET LIVE ATE_PAD TOOLING4.1 TOOLING4.1 HP007 R527 EARTH...

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