Arcam DiVA DT81 Manuale di servizio - Pagina 3

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DT81 Circuit Description

Summary

The L918 forms the basis of the DT81 DAB tuner. All the circuitry

of the tuner is on the same board, with the exception of the front

panel PCB.

The tuner is based on the Roke Manor gold card which provides the

RF receiver and DAB decoding. To accompany this module the DAB

motherboard

has

various

microcontroller, a D-A converter with output buffer, and an SPDIF

transmitter.

Power supplies and muting

The mains transformer T1 is used for 230V and 115V operation, the

voltage selection is done by fitting different fuses. F1 160mA is

fitted for 230V and F2 250mA for 115V.

The front panel board is powered from the 7.5V unregulated supply

(it has its own regulator). The digital supplies are switched by SW3,

while the analogue supplies are on all the time while the mains is

connected.

Regulated supplies

P15V, N15V. +/-15V for the output buffer and DAC 5V regulator.

P5VDAC. +5V supply for DAC.

P5VDAB. 5V supply for DAB module.

P5V. +5V supply for digital circuits - Micro and SPDIF transmitter.

P10V. +10V supply for DAB module.

P7V5_UR. Unregulated 7.5V supply goes to front panel.

Z9 is a Toshiba TA7317. This controls the muting/bypass relay. The

same relay is used for power on/off muting and also FM tuner bypass

mode.

The muting circuit has a time constant of 2.5 seconds, so there is

always a 2.5 second delay when un-muting the output.

The FM tuner bypass switch is shown on this sheet (SW2) and is

accessed from the front of the unit.

Micro, DAB module, SPDIF

Z204 is a Hitachi H8/3048F 16 bit microcontroller. It has FLASH

program memory, and is programmed via header SK1. Z202 is a

64kbit parallel EEPROM used for storing multiplex data. this is

where the system stores data about the multiplexes it finds when it

does a search, and other information (presets, compression level, sort

type, display mode).

Z205 is a 3 pin reset generator IC. SW1 is a latching push switch

accessed from the rear of the unit. If the switch is pushed in,

RDI_ON will be low. This has the effect of removing data services

from the list of services. If the switch is left out, RDI_ON will be

high and the data services can be seen.

SK3 is used to connect to the front panel, communication is done via

the I2C bus. Power for the front panel comes in the form of

P7V5_UR. Note that although P5V connects to the front panel, it is

not used for power. Its purpose is to light the front panel LED green.

DAB module: JP1 is a 50 way SAMTEC connector which provides

the interface to the Roke DAB module. All the I/O to the module is

on this connector apart from the aerial input which has a cable going

straight from the rear panel to the module.

Communication between the micro and the DAB module is done via

the serial port of each device on TX_DAB/RX_DAB.

The digital audio output from the module comprise of MCLK

(12.288MHz master clock), LRCK (48kHz left/right clock), SCLK

(serial data clock) and SDATA (serial data).

These signals go to the D-A converter, and also to the SPDIF

transmitter Z201.

power

supplies,

Hitachi

Z201 is the SPDIF transmitter. Each one of the differential ouputs is

used separately. SPDIF_OP is for the optical output, SPDIF_CX is

for the coax output.

DAC

Z101 is a CS4327 D-A converter, followed by filter/buffer Z102.

This is followed by ac coupling capacitors. The relay RLY1 is the

last stage before the phono output connectors. 2 stereo outputs are

provided on SK101. SK102 is an input which gets routed through the

relay when the relay is off.

An external FM tuner can be connected to this, in order to avoid

taking up an extra input on the amplifier. When the tuner is off or in

bypass mode, the FM tuner is routed to the output.

The digital audio outputs are also shown on this sheet. TX101 and

associated components provide an isolated unbalanced SPDIF output

on SK103, and Z4 produces an optical output.

Software notes

The system has non volatile storage in the form of the EEPROM,

Z202. The following information is stored there and is remembered

at power up:-

Service data - all the IDs and static prog types of the services

available in the ensembles found in the last search. This is the

information viewed when turning the knob.

Service selected - last service selected.

Display mode - prog type, dynamic label, data rate or signal quality.

Display brightness - off, dim or bright.

Compression level - off or 1-5.

The following parameters are NOT remembered:-

Engineering mode. If the unit is turned off while in engineering

mode (or test mode), it will default back to user mode on power up.

Bypass mode - the unit will always power up not in bypass mode.

Secondary services - if a secondary service is selected when it is

switched off, it will power up with the parent service selected.

Erasing the EEPROM - to erase the EEPROM, go into engineering

mode (SELECT +8), then hold down preset buttons 1,4,5,8. The

display will say 'ERASING EEPROM' followed by 'PASSED

EEPROM TEST' then 'EEPROM ERASED'. If you switch the

power off and on again, it will come on with all the parameters reset.

Display mode - prog type

Display brightness - bright

Compression - off.

Selection Mode – manual

Test mode

If you hold in the bypass button while powering up, this will put the

unit in test mode. When the bypass button is released, the software

version will be displayed. Pressing the front panel buttons will cause

a message to be displayed. Turning the knob clockwise or

anticlockwise will cause a message to be displayed. Any RC5 remote

commands will also be displayed, with command and system codes,

and an asterisk for the toggle bit.

Fault mode

On switch on if the Roke module is not fitted, or if there is a problem

with the RX or TX communication signal between the module and

the H8, the unit displays 'ERROR CIP FAILURE'.