Onkyo A-8850 Service Manual

A-8850
ADJUSTMENT PROCEDURES
Adjustments and Checking the Protection Circultry
1. Preparations
1)
Place
the
unit
on
the
workbench.
(There
should
be
about
15
mm
of
space
between
the
base
plate
of
the
unit
and
the
work
surface.)
2) Set up the unit as follows.
(1) No load
(2) No signal
(3) Volume turned all the way down
(4) Speaker switch OFF
(5) Power switch OFF
Note) Check the following points before making adjustments
(1) The power switch should be OFF.
(2) The interior of the unit should not be warm.
2. Idling current adjustment
1)
Turn
the
power
switch
ON
and
allow
the
unit
to
warm
up
for
about
10
minutes.
(1)
Adjust
R535
(R536)
so
that
the
voltage
at
test
point
VCT-ITD
on
the
NAAF-4209
circuit
board
is
1SmV+t5mV.
Note)
Semi-fixed
resistors
enclosed
in
parentheses
(_
)
are
for
the
right
channel.
3. Check of operation of protection circuitry
1) Check of operation of protection relay
(1)
Confirm
that
the
relay
turns
ON
approximately
5
seconds
after
the
power
switch
is
turned
ON.
(2) The SERVO indicator LED should light at the same time.
(3)
The
relay
should
turn
OFF
approximately
0.5
seconds
after
the
power
switch
is
turned
OFF.
2) Check of DC detection and servo circuitry operation
(1) Turn the power on with no load.
(2)
After
the
speaker
relay
turns
ON,
apply
DC+200mV
to
the
CD
input
terminals.
Confirm
that
the
relay
turns
OFF.
(3)
Confirm
that
operation
is
the
same
as
(2)
above
when
an
input
of
DC—200mV
is
applied.
Note)
Under
no
circumstances
connect
a
load
or
short
the
speaker
terminals
when
performing
the
above
test.
3) Signal input from the circuit illustrated below with no load.
(1)
Confirm
that
the
speaker
relay
does
not
turn
OFF
even
when
a
2
ohm
load
is
connected
when
a
peak
value
of
30Vp
is output.
(2)
Next,
confirm
that
when
a
1
ohm
load
is
connected
the
speaker
relay
switchse
OFF
and
ON
a
couple
of
times
and then stays OFF.
Note)
The
period
before
that
relay
stays
OFF
should
not
last
for
more
than
1
minute,
Relay
OFF
status
can
be
canceled
by
switching
the
power
OFF.
Low-frequency
oscillator Auplifier
SP Load
OUT aes
Differe-
atiator
Attenua-
tor
Square wave The unit’s volume
50Hz, 10 p-p control way also
be used.
3.3 KQ O.1 uF 3.3 KQ OUTPUT
Square wave input from
low-frequency oscillator 10 KQ
50 Hz, 10V p-p
Ws

Onkyo A-8850 Specifications

General

Input Sensitivity (MM)	2.5 mV
Total Harmonic Distortion	0.008%
Input Sensitivity	150 mV (line in)
Dimensions	435 x 171 x 398mm (W x H x D)
Damping Factor	50
Signal to Noise Ratio (MM)	80 dB
Speaker Load Impedance	4 ohms minimum
Speaker Impedance	4Ω-16Ω
Tone Control	Bass, Treble