Arcam DiVA DT81, Service Manual

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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 power supplies, a Hitachi H8
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.
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 (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’.