Arcam Alpha 9 Service Manual - Page 2

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ALPHA 9/9P SERVICE MANUAL

The optional phono stage board available for the

Alpha

provides

equalization for both moving coil (MC) and moving

magnet (MM) cartridges.

Transistors Q2-5 and their associated components

provide the extra gain required for moving coil

cartridges when required Z1 forms a flat response

gain stage with the gain set by R3 and R4. R5 and

C2 provide a low pass filter used as the high

frequency part of the RIAA de-emphasis.

negative feedback loop around IC2, R7, 8, 9, 10

and C3 provides the active low frequency RIAA de-

emphasis.

The pcb mounted switch selects between MM or MC.

The board is powered by +/- 15V regulated rails from

the main pcb and the +15V rail is then regulated to

6.3V by Q1 and D1, D2 to power the moving coil

stage.

TEST POINT

DC VOLTAGE

TP1

+ 5V

TP2

+9.6V

TP3

0V MUTE ON +2V MUTE OFF

TP4

0V VOL UP +5V VOL DOWN

TP5

+5V VOL UP 0V VOL DOWN

TP6

+15V

TP7

-15V

TP8

+44V

TP9

-44V

amplification

and

RIAA

The

Disassembly For Servicing

Remove the top cover and front panel.

Remove 2 screws securing the sub front to the

chassis sides and 3 screws holding the

subfront to the chassis base.

Remove 3 screws

chassis. These can be found close to the large

heatsink and also near to the mains inlet

socket.

Remove 5 screws from the rear panel, one at

each end and 3 along the bottom edge.

Remove the transformer bolt.

The pcb,

with the rear panel, transformer and

subfront attached, can now be pulled backwards out

of the unit.

TEST POINT

DC VOLTAGE

TP10

0.5V

TP11

0.5V

TP12

-2V

TP13

-2V

TP14

+2.2V

TP15

+2.2V

TP16

+6.8V

TP17

0V MUTE ON +2V MUTE OFF

The IQ voltage measured across the 0.22 ohm

resistors R1, RA1 or R101, RA101should be about 6-

7 mV.

holding the pcb to the