Arcam DiVA CD62 Manuale di servizio - Pagina 3

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CD62 (text) Circuit Description

Summary

The main Motherboard/Display PCBs for the Diva CD players

may be assembled as three different versions:

DiVA CD62 (text) - With alternate components fitted

and the 92DAC upgrade connections omitted

(L933AY).

DiVA CD72 (text) - With the standard set of

components fitted (L899AY).

DiVA CD92 (text) - With analogue components and

connectors omitted, for use as a host motherboard for

the plug-in 92DAC (L934AY).

All systems are based on a Sony kit, comprising CDM14BL-

5BD25 CD transport / loader / laser mechanism, micro-controller

and fluorescent display.

Power Supplies

The CD62 may be fitted with any of the following transformers

dependant on supply voltage required:-

230VAC only - part number L849TX

115VAC only - part number L850TX

100VAC only - part number L851TX

Later models are fitted with L867TX which is a 230/115VAC

transformer.

The mains transformer has three secondary windings:

13.7V – 0V – 13.7V to provide ±12V(A) supplies

(IC201 and IC205) for the audio output circuitry via

regulators IC201 and IC205.

9V-0V-32V to produce the digital, motor drive and

fluorescent display grid supplies:

+11V(U) Unregulated supply for relay drive and

+5V(D) supply

+7V

(IC200) Mechanism and motor driver

supply

+5V(D)

(IC202) General digital logic supply

+5V(A)

(IC203) Supply to DAC

-30V

(IC204) Display grid voltage.

0-5V to provide an AC supply for the display

filament.

Relay Mute Control

This circuit drives a relay to un-mute the analogue output ~5

seconds after the unit is powered on, and quickly mutes the

output when the unit is switched off. The circuit works

effectively as an "AND" gate.

If AC is present on the transformer secondary winding and the 5-

second timer composed of R222 and C221 has reached the

threshold voltage (Vbe of TR200 + Vbe of TR201 - Vce of

TR202, or ~1.0V), the relay coil is connected to +11V

(referenced to 0V_3 as required by the 9DAC's internal circuitry)

via TR204.

When AC is removed, C231 discharges quickly through R225,

the base voltage of TR204 rises and the relay coil voltage is

removed, muting the output.

TR203 resets the 'timer' by discharging C221 quickly at turn-off.

Remote Control/PIC Micro

Remote control data is received from the IREye on the display

PCB and buffered by TR300 and TR301. The Programmable

Interrupt Controller converts the RC-5 format data into the NEC

format required by the Sony micro.

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 IC303.

Clock Buffering

The clock and data signals LRCK, ADATA and BCLK from the

mechanism connector SK300 are double buffered by IC300

before being delivered to the DAC.

Power-On/Reset

The power-on reset signal XRST (or RESET) is generated by

R409, C410 and IC404. When the power is turned on, C410 is

initially uncharged and pin 11 of IC404 is at high voltage, and

thus the output is low. After a short time, C410 is charged via

R409; IC404 pin 11 is then low, and the output switches high

(RESET is de-asserted).

DAC & System Clock

The DAC is a Burr Brown PCM1716E, the DAC is configured

for hardware control.

Digital audio is input on pins 1, 2 & 3 in standard Red Book

Audio format, i.e. Word Clock, Bit Clock and Data.

The system clock is based around 16.9344 MHZ crystal X400

and transistor TR402. This produces a stable clock with low

jitter. IC404A & B buffer the clock as linear buffers. IC404C &

D buffer the individual mech & DAC clock lines.

Analogue Output

Left channel:

IC400A and IC400B are cascaded 69kHz 2

Bessel filters. The output devices internal to both op-amps in

IC400 are "pulled down" to the negative supply rail to force

operation in class A (one output device is conducting at all times

and crossover distortion is eliminated).

C448 AC-couples the output, the muting relay shorts the output

to ground through 120 ohm series resistors, and 3N3

Polypropylene shunt capacitors are used to swamp cable

capacitance, ensuring stability and making up the 5

filter.

The right channel is the same as the left channel. IC401A & B

are used as the buffer and filter.

order low-pass

pole of the