FAULT
FINDING
©
Cyrus
Audio
Ltd
Jun
2014
12
Cyrus
6
DAC,
Cyrus
8
DAC
service
manual
Issue
1
The
amplifiers
are
complex,
microcontrolled
products
using
small
‐
scale
SMD
technology.
Do
not
attempt
any
fault
‐
finding
or
repair
on
one
of
these
products
unless
you
are
a
competent
audio
engineer
with
the
correct
SMD
repair
tools
and
trained
to
fault
‐
find
on
this
equipment.
This
fault
‐
finding
guide
is
not
exhaustive,
but
should
help
a
competent
engineer
trace
faults
within
the
amplifier.
If
you
require
more
technical
help
than
this
guide,
contact
the
Cyrus
Service
Department.
CAUTION
The
high
‐
efficiency
heat
‐
transfer
insulation
pads
fitted
between
the
power
amplifier
output
transistors
and
the
chassis
of
the
amplifiers
are
designed
to
soften,
melt
and
bond
to
the
transistor
and
heatsink
when
the
amplifier
first
heats
up.
This
is
to
enable
the
pads
to
fill
any
pits
in
the
surface
of
the
heatsink
and
provide
an
excellent
thermal
bond
between
the
transistor
and
heatsink.
For
this
reason
any
pad
material
must
ALWAYS
be
completely
scraped
from
the
heatsink
and
the
pads
replaced
if
the
seal
is
broken
between
the
transistor
and
heatsink,
as
they
will
not
re
‐
bond.
Conventional
pads
and
grease
are
much
less
efficient
heat
conductors
and
are
not
an
acceptable
substitute
for
the
correct
pads.
Use
of
alternative
pads
will
risk
future
failure
of
the
amplifier.
Always
obtain
original
pads
from
the
Cyrus
Service
Department.
Layout
of
the
amplifier
The
amplifier
is
constructed
with
the
analogue
pre
‐
amplifier,
power
amplifier
and
power
supply
laying
on
the
main
PCB
fixed
in
the
base
of
the
chassis,
and
a
smaller
sub
PCB
located
over
this
that
includes
the
headphone
amplifier,
the
power
supply
for
the
display
backlight,
the
circuitry
for
the
digital
inputs
and
the
D/A
converter.
The
analogue
audio
output
from
the
digital
audio
section
of
the
sub
PCB
connects
to
the
preamplifier
on
the
main
PCB
through
a
cable.
The
circuitry
that
controls
the
amplifier
is
located
on
the
front
panel
PCB
with
the
LCD
display.
Dismantling
the
amplifier
Basic
tests,
alignment
and
fuse
replacement
are
possible
without
removing
the
sub
PCB.
All
alignment
test
points
on
the
main
PCB
and
the
right
channel
adjustment
presets
are
accessible
around
the
border
of
the
sub
PCB.
The
left
channel
adjustment
presets
can
be
reached
through
an
access
hole
in
the
sub
PCB.
For
access
to
test
or
repair
the
preamplifier
or
power
amplifier
stages,
the
sub
PCB
must
first
be
removed.
With
the
sub
PCB
removed,
the
amplifier
will
continue
to
function
as
normal
for
test
and
repair,
but
without
the
display
backlight
or
digital
inputs.
The
sub
PCB
cannot
simply
be
unplugged
from
its
main
PCB
connector
without
damage.
To
remove
the
sub
PCB
leaving
the
main
PCB
in
the
chassis,
remove
the
screws
securing
the
rear
panel
to
the
sub
PCB
and
the
two
along
the
top
edge
fixing
it
to
the
chassis.
Remove
the
nut
securing
the
headphone
socket
(special
tool
required).
Once
the
screws
are
removed,
the
rear
panel
can
be
tilted
back
slightly
to
allow
clearance
to
remove
the
sub
PCB
from
its
connector.
CAUTION:
When
re
‐
fitting
the
sub
‐
PCB,
take
particular
care
to
ensure
that
the
connector
pins
are
correctly
aligned.
Misalignment
of
the
pins
will
cause
considerable
damage
to
the
sub
‐
PCB.
Initial
precautions
and
first
tests
Before
connecting
power
to
an
amplifier
that
is
suspected
to
be
faulty,
ensure
that
loudspeakers
and
loads
are
disconnected
from
the
speaker
sockets
to
avoid
damaging
them.
