Arcam Alpha 8-R Service manual

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUALALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL

Arcam Alpha One/ 7R/ 8R/ 8P Amplifier Service Manual

Issue 1 Serial Number 001 - (Paul Newton/ Haider Bahrani Sept ‘98)

Circuit Description

The Alpha One / 7R/8R and 8P share a common pcb. The circuits are very similar and the main differences are the remote volume facility and extra power output on the 7R and 8R and a switch to bypass the phono stage to enable its use as an extra line level input and the AV processor switch on the Alpha 8R integrated amplifier. The 8P power amplifier utilises the same power amplifier circuit as the Alpha 8R integrated amplifier.

Power Supplies

The ac output of the toroidal mains transformer is rectified and smoothed by D201-204 and C204, 205. This is then regulated to +/-15V by Z201, 202 to power the phono and tone control stages and the d.c. servo.

The Alpha 7R and 8R transformers have an extra tapping which is used for the remote volume circuit. The ac in is regulated to 5V by zener D902 and associated components and this is then used to power the microcontroller Z901 and remote receiver.

Phono Stage (Not applicable to Alpha One) The phono stage consists of a dual opamp Z305, one

opamp per channel. The RIAA equalization is achieved by the feedback components R703, 704, 702 and C704, 705, 702 on left channel (R603 etc. as above for Right channel). R703 determines the gain and C703 the low frequency roll off.

On the Alpha 8R this stage can be bypassed by use of switch SW302 to enable use as an extra line input.

Tone Controls

source for the differential input stage. The output devices are 'n' channel mosfets SMF045.

Zener diodes D103,104 limit the voltage swing within safe limits for the output devices & fusible resistors R105, 106 provide overcurrent damage to the devices.

A proportion of the output current appears across the protection network R41,42. If this becomes too high Q17 is turned on and mutes the output. High D.C. levels at the output will also mute the output. There are no output fuses on the Alpha One, 7R and 8R/8P amplifiers. The muting is done by the mute ic Z303 and its associated compontents. The mute operates on switch on/off and if an over current or over voltage condition occurs. The power led glows amber when the mute circuit is operative and glows green in normal use.

Removing the Alpha One/ 7R/ 8R/ 8P Transformer

The toroidal transformer is extremely well secured to the main pcb with a double sided adhesive gasket. To remove the transformer you must break this adhesive bond by cutting through the gasket. This will be easier if the transformer is warm. Use a cheese wire under the transformer, pulling backwards and forwards under tension to gradually cut through. Once most of the adhesive is cut, you should be able to pull the transformer away from the pcb.

A less satisfactory substitute for cheese wire is to use some 22 gauge tinned copper wire, stretched first to remove kinks, and two temporary handles.

Alpha One/7R/ 8R/ 8P Quiescent Current (IQ) Settings

The tone control stage is based around Z304 a dual op amp. The range of the controls is set by R507, 508 for the bass pot RV302 and R509, 510 for the treble pot RV303. The tone controls and balance pot can be bypassed by use of the direct switch, SW304.

Power Amplifier

The input to the power amplifier from previous stages is fed to the differential input of Q112 and Q113. Q110 and Q111 form a constant current

When replacing the output transistors of the above amplifiers it is important to reset the quiescent current (IQ) to the correct value to prevent the amplifier blowing again.

The IQ should be checked and set by following the procedure below:

From cold and with no load or signal connected Turn both IQ presets (RV1 and RV101) down to minimum (fully anticlockwise) and set the voltage drop across resistor R1 (R101 for right hand channel) to between 3.0 and 3.5mV for the Alpha One and 7R

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUALALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL

amps or between 2.3 and 2.8mV for the Alpha 8R/8P amps.

Leave the unit for 1 minute and reset to these values if required.

Leave the unit for a further 5 minutes and reset if required.

The IQ is now set and the unit can be connected to speakers and fully checked out.

TEST POINT VOLTAGES

Test Point DC Voltage Alpha One DC Voltage Alpha 7R DC Voltage Alpha 8R/8P 1 32.8V 35V 37V

Disassembly For Servicing

1. Remove the top cover and front panel.

2. Remove 2 screws securing the sub front to the chassis sides and 3 screws holding the subfront to the chassis base.

3. Remove 1 screw holding the pcb to the chassis. This can be found near to the mains inlet socket.

4. Remove 5 screws from the rear panel, one at each end and 3 along the bottom edge.

5. Remove the transformer bolt.

6. Release the PCB pillar located near to the serial number on the pcb.

The pcb, with the rear panel, transformer and subfront attached, can now be pulled backwards out of the unit.

2 27.8V 29V 31V 3 15V 15V 15V 4 -32.8V -35V -37V 5 27.8V -29V -31V 6 -15V -15V -15V 7 N/A 0.09V 0.09V 8 N/A 0.10V 0.10V 9 0.3V 0.27V 0.27V 10 3.4V 3.2V 2.9V 11 32.8V 35V 37V 12 -3V -2.7V -2.5V 13 32.8V -35V -37V Between 14 & 15 3.0 -3.5mV 3.0-3.5mV 2.3-2.8mV 16 (protection off) 0.0V 0.0V 16 (protection on) 0.6V 0.6V 17 0.0V 0.0V 18 0.0V 0.0V 19 0.0V 0.0V

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUALALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL

Test Point DC Voltage Alpha One DC Voltage Alpha 7R DC Voltage Alpha 8R/8P 20 0.0V 0.0V 0.0V 21 (protection off) 1.6V 1.6V 1.6V 21 (protection on) 5.0V 5.0V 5.0V 22 0.58V 0.17V 0.17V 23 3.4V 3.1V 3.1V 24 -3V -2.7V -2.7V 25 -26V -29V -29V Between 26 & 27 3.4mV 3.4mV 2.5mV 28 (muted) 35V 35V 35V 28 (protection off) 1V 1V 1V 29 N/A 5V 5V 30 N/A 10.5 10.5V 31

N/A 0V 0V

(volume going up) 31

N/A 5V 5V

(volume going down) 32

N/A 0V 0V

(volume going up) 32

N/A 5V 5V

(volume going down)

PARTS LISTS

The parts for all the units are as the Alpha 7 except where shown.

REF Description Part No Product

C1 ELST 100U 100V 2N710B 7R

C2 PEST 47N 63V 10% 2K347 7R

C3 PCRB 100N 100V 5% RA

C4 PEST 47N 63V 10% 2K347 7R

C5 PSTY 33P 160V ENCAP

C7 PPRO 4N7 63V 5% RA 2D247N 7R

C8 PPRO 100P 63V 5% RA 2D110N 7R

C9 ELST 100U 25V 2N710 A1

C10 ELST 22U 20V OSCON 2P622 7R

C10 ELST 22U 63V ELECT 2N622 A1

C11 ELST 100U 100V 2N710B 7R

C12 ELST 100U 100V 2N710B 7R

C13 PEST 15N 63V 10% 2K315 7R

C14 PEST 15N 63V 10% 2K315 7R

5mm

1PF%

2H410 7R

2F033 7R

C15 SUPPR CAP 4N7 250V 2K247 7R

C16 ELST 100U 25V 2N710 7R

C17 CERD 470P 63V 20% RA 2A147 7R

C18 CERD 1N0 63V 20% RA 2A210 7R

C19 ELST 100U 25V 2N710 7R

C20 CERD 470P 63V 20% RA 2A147 7R

C21 CERD 10N 63V 20% RA 2A310 7R

C22 CERD 10N 63V 20% RA 2A310 7R

C23 SUPPR CAP 4N7 250V 2K247 7R

C24 PPRO 4N7 63V 5% RA 2D247N 7R

C25 PCRB 100N 100V 5% RA

C26 PCRB 100N 100V 5% RA

C27 ELST 220U 16V 2N722 7R

C28 PCRB 100N 100V 5% RA

5mm

2H410 7R

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUALALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL

C29 ELST 1U0 50V 20% RA 2N510 8R

C30 ELST 22U 63V ELECT 2N622 7R

C30 ELLL 47U 10V ELECT 2R647 A1

C30 ELEC 10U 25V CERAFINE 2P610CC 8R

C101 ELST 100U 100V 2N710B 7R

C102 PEST 47N 63V 10% 2K347 7R

C103 PCRB 100N 100V 5% RA

C104 PEST 47N 63V 10% 2K347 7R

C105 PSTY 33P 160V ENCAP

C107 PPRO 4N7 63V 5% RA 2D247N 7R

C108 PPRO 100P 63V 5% RA 2D110N 7R

C109 ELST 100U 25V 2N710 A1

C110 ELST 22U 20V OSCON 2P622 7R

C110 ELST 22U 63V ELECT 2N622 A1

C111 ELST 100U 100V 2N710B 7R

C112 ELST 100U 100V 2N710B 7R

C113 PEST 15N 63V 10% 2K315 7R

C114 PEST 15N 63V 10% 2K315 7R

C116 ELST 100U 25V 2N710 7R

C117 CERD 470P 63V 20% RA 2A147 7R

C118 CERD 1N0 63V 20% RA 2A210 7R

C119 ELST 1U0 50V 20% RA 2N510 7R

C120 CERD 470P 63V 20% RA 2A147 7R

C121 ELST 1U0 50V 20% RA 2N510 7R

C122 ELST 100U 25V 2N710 7R

C123 ELST 100U 25V 2N710 7R

C124 PPRO 4N7 63V 5% RA 2D247N 7R

C125 PCRB 100N 100V 5% RA

C126 PCRB 100N 100V 5% RA

C127 ELST 220U 16V 2N722 7R

C128 PCRB 100N 100V 5% RA

C130 ELST 22U 63V ELECT 2N622 7R

C130 ELLL 47U 10V ELECT 2R647 A1

C130 ELEC 10U 25V CERAFINE 2P610CC 8R

C200 CERD 1N0 63V 20% RA 2A210 7R

C201 SUPPR CAP 4N7 250V 2K247 7R

C204 ELST 10m 50V RA 32mm 2N910 7R

C204 ELST 6M8 35V RA 2N868 A1

C205 ELST 10m 50V RA 32mm 2N910 7R

5mm

1PF%

5mm

2H410 7R

2F033 7R

2H410 7R

C205 ELST 6M8 35V RA 2N868 A1

C206 PCRB 100N 100V 5% RA

C207 PCRB 100N 100V 5% RA

C208 PPRO 4N7 63V 5% RA 2D247N 7R

C209 PPRO 4N7 63V 5% RA 2D247N 7R

C210 ELST 10U 50V 2N610 7R

C211 ELST 10U 50V 2N610 7R

C212 CERD 10N 63V 20% RA 2A310 7R

C213 CERD 10N 63V 20% RA 2A310 7R

C214 CERD 10N 63V 20% RA 2A310 7R

C215 CERD 10N 63V 20% RA 2A310 7R

C216 CERD 10N 63V 20% RA 2A310 7R

C217 CERD 10N 63V 20% RA 2A310 7R

C301 CERD 10N 63V 20% RA 2A310 7R

C302 CERD 10N 63V 20% RA 2A310 7R

C502 PCRB 100N 100V 5% RA

C303 CERD 1N0 63V 20% RA 2A210 7R

C304 CERD 1N0 63V 20% RA 2A210 7R

C305 CERD 47P 63V -20% +80%RA2A047 7R

C306 CERD 47P 63V -20% +80%RA2A047 7R

C401 ELST 10U 50V 2N610 7R

C402 PEST 220N 63V 10% 2K422 7R

C402 PCRB 100N 100V 5% RA

C403 PCRB 100N 100V 5% RA

C403 PEST 220N 63V 10% 2K422 7R

C404 PPRO 4N7 63V 5% RA 2D247N 7R

C404 2N2 PP 2D222 A1

C405 ELST 10U 50V 2N610 7R

C406 CERD 100P 63V 20% RA 2A110 7R

C407 CERD 100P 63V 20% RA 2A110 7R

C408 CERD 10P 63V 20% RA 2A010 7R

C501 ELST 10U 50V 2N610 7R

C502 PEST 220N 63V 10% 2K422 7R

C503 PEST 220N 63V 10% 2K422 7R

C503 PCRB 100N 100V 5% RA

C504 PPRO 4N7 63V 5% RA 2D247N 7R

C504 2N2 PP 2D222 A1

C505 ELST 10U 50V 2N610 7R

5mm

2H410 7R

2H410 A1

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUALALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL

C506 CERD 100P 63V 20% RA 2A110 7R

C507 CERD 100P 63V 20% RA 2A110 7R

C508 CERD 10P 63V 20% RA 2A010 7R

C601 PPRO 100P 63V 5% RA 2D110N 7R

C602 CERD 47P 63V 20% RA 2A047 7R

C603 ELST 22U 63V 2N622 7R

C604 PPRO 4N7 63V 5% RA 2D247N 7R

C605 PPRO 1N3 63V 5% RA 2D213N 7R

C606 ELST 10U 50V 2N610 7R

C701 PPRO 100P 63V 5% RA 2D110N 7R

C702 CERD 47P 63V 20% RA 2A047 7R

C703 ELST 22U 63V 2N622 7R

C704 PPRO 4N7 63V 5% RA 2D247N 7R

C705 PPRO 1N3 63V 5% RA 2D213N 7R

C706 ELST 10U 50V 2N610 7R

C801 PPRO 100P 63V 5% RA 2D110N 7R

C802 PPRO 100P 63V 5% RA 2D110N 7R

C803 ELST 10U 50V 2N610 7R

C804 ELST 10U 50V 2N610 7R

C805 CERD 10N 63V 20% RA 2A310 7R

C806 CERD 10N 63V 20% RA 2A310 7R

C901 CERD 10N 63V 20% RA 2A310 7R

C902 ELST 220U 16V 2N722 7R

C903 CERD 10N 63V 20% RA 2A310 7R

C904 CERD 10N 63V 20% RA 2A310 7R

C905 CERD 10N 63V 20% RA 2A310 7R

C906 CERD 10N 63V 20% RA 2A310 7R

C907 ELST 1M0 25V 2N810 7R

C1000 CERD 10N 63V 20% RA 2A310 7R

CL1 ALPHA AMP 7/8 HEATSINK

CL2 ALPHA AMP 7/8 HEATSINK

D1 RECTIFIER 1N4003F 1A

D2 ZENER 10V 400MW 3C11004 7R

D3 ZENER 10V 400MW 3C11004 7R

D4 ZENER 10V 400MW 3C11004 7R

D5 SSDIODE 1N4148 75V 3A4148 7R

D6 RECTIFIER 1N4003F 1A

D7 SSDIODE 1N4148 75V 3A4148 7R

D8 RECTIFIER 1N4003F 1A

CLAMP

200V

E82201 7R

3B4003 7R

3B4003 8R

3B4003 7R

D9 RECTIFIER 1N4003F 1A

D10 ZENER 5V6 400MW 3C05604 8R

D101 RECTIFIER 1N4003F 1A

D102 ZENER 10V 400MW 3C11004 7R

D103 ZENER 10V 400MW 3C11004 7R

D104 ZENER 10V 400MW 3C11004 7R

D105 RECTIFIER 1N4003F 1A

D106 RECTIFIER 1N4003F 1A

D107 RECTIFIER 1N4003F 1A

D108 ZENER 5V6 400MW 3C05604 7R

D201 ULTRAFAST RECTIFIER

D202 ULTRAFAST RECTIFIER

D203 ULTRAFAST RECTIFIER

D204 ULTRAFAST RECTIFIER

D801 ZENER 5V6 400MW 3C05604 7R

D802 ZENER 4V7 400MW 3C04704 7R

D803 SSDIODE 1N4148 75V 3A4148 7R

D901 RECTIFIER 1N4003F 1A

D902 ZENER 5V6 400MW 3C05604 7R

D903 RECTIFIER 1N4003F 1A

D904 ZENER 5V6 400MW 3C05604 7R

D905 SSDIODE 1N4148 75V 3A4148 7R

EL1 FUSE CLIP WCK-180-01A F062 7R

FS201 INS COVER PCB

FS201 FUSE 20mm 1.25A AS C12126 7R

FS201 FUSEHOLDER 20mm PCB 8S004 7R

FS202 FUSEHOLDER 20mm PCB 8S004 7R

FS202 INS COVER PCB

HS1 ALPHA AMP 7/8 HEATSINK E81801 7R

HS1 SIL PAD - 25 X 12.5mm E817MC 7R

HS1 ALPHA AMP 7/8 HS CLIP E810MC 7R

HS2 SIL PAD - 25 X 12.5mm E817MC 7R

HS2 ALPHA AMP 7/8 HEATSINK E81801 7R

HS2 ALPHA AMP 7/8 HS CLIP E810MC 7R

HS3 SIL PAD - 25 X 12.5mm E817MC 7R

200V

DIODE UF5403 3A

200V

FUSEHOLDER

3B4003 7R

3B5403F 7R

3B4003 7R

F022 7R

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