Circuit Description; Power Supplies & Reset/Mute; Micro Controller & Display Board; Dac & System Clock - Arcam DiVA CD72 Service Manual

CD72/CD92 Circuit Description
SUMMARY
The Main PCB for the DiVA CD72/92 player may be built as
two different versions:
!
With all components fitted for the Alpha CD72
(L887RS)
!
With audio components and connectors omitted, for
use as a motherboard for plug-in DAC module L816
(L888RS) for CD92
The CD72 version may be converted for use with a upgrade
plug-in DAC board by removing a configuration connector.
The system is based on a Sony kit, comprising CDM14-5BD10
laser mechanism & loader, micro-controller and fluorescent
display.
The PCM 1716, as per the 1710, can be operated in either
Software or Hardware mode. The default for the CD72 is
hardware mode.
Power Supplies & Reset/Mute
Selection for 230V or 115V mains operation is made by
inserting a fuse into the appropriate position. The mains
transformer has three secondary windings:
1. Provides +12V and -12V supplies for the audio
output circuitry via regulators Z204 and Z205.
2. This produces the digital, motor drive and
fluorescent display grid supplies:
+7.3V (Z206) Mechanism and motor driver supply
+5V (Z208) General digital logic supply
+5V (Z207) Supply to DAC
+5V (Z203) Supply to system clock generator
-30V (Z209) Display grid voltage.
3. Provides an AC supply for the display filament.
The power-on reset signal XRST is generated by R17 and C29.
When the power switch is turned off one of its poles discharges
C29 quickly. This, along with the AMUTE signal from the
micro, controls the output mute transistors via level shifter Q3.
Remote Control/PIC Micro
The PIC micro controller converts the RC-5 format data into the
NEC format required by the Sony micro. The PIC also controls
the configuration of the digital filter/DAC on the DAC board.
Micro controller & Display Board
The system micro controller Z212 has the following functions:
!
Control of the mechanism & decoder on the CDM14
!
Control of mute, attenuation and deemphasis for the
DAC
!
Direct drive of the fluorescent display
!
Remote control decoding
!
Keyboard scanning
The keyboard scanning works by connecting the keys to a
resistor ladder on an ADC input to the micro. Pressing a key
presents a unique voltage to this input.
The remote control data contains a 'Customer Code' that
identifies this as an Arcam product. The diode network D291 to
D297 configures the micro to accept this code.
Motor Driver
The status of the drawer is indicated to the micro by two micro
switches 'INSW' and 'OUTSW' on SK205. The micro controls
the drawer motor via driver Z210.
DAC & System Clock
The DAC is a Burr Brown PCM1716. Mute, attenuation and de-
emphasis functions can be controlled via a 3-wire serial link
from the system micro to pins 26, 27 & 28 via resistors R31 R32
& R33 respectively. Currently resistors R31 to R33 are not
fitted and the DAC is configured for hardware control.
Digital audio is input on pins 1, 2 & 3 in standard Sony format,
i.e. Word Clock, Bit Clock and Data.
The system clock is based around 16.9344 MHZ crystal X1 and
transistor Q2. This produces a stable clock with low jitter.
Z202E & D provide amplification and buffering to the DAC.
Analogue Filters
Z1A (& Z101A) provides the basis for a 2-pole filter. Z1B (&
Z101B) buffer the audio and set the output level.
Digital Output
An SPDIF format digital output signal is generated by the
decoder on the mechanism assembly. This is passed through
isolating transformer T202 to a single phono socket SK5.
Optical digital output via Z2 is also tapped off the digital output
signal. Power is supplied to Z2 via Z3 a 78L05 regulator.
Upgrade to CD92
The CD72 includes a configuration PCB connected to PL1. This
provides power to the DAC and clock generator, connects the
digital audio and system clock signals to the DAC and provides
additional clock buffering with Z4 A&B .
Removing this board removes these connections and allows the
system clock generated on the DAC board to pass through to the
CDM14.