Onkyo A-8870 User Manual

A-8870
ADJUSTMENT PROCEDURES
Adjustments and Checking the Protection Circuitry
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-IID
on
the
NAAF-4209
circuit
board
is
I5mV+5mV,
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 oftames
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 : resistance
Differe-
ntiator
Attenua~
tor
Square wave The unit’s volume
50Hz, 1!0V¥ p-p control may also
be used. Oscillo-
scope
3.3 KQ 0.1 uF 3.3 KQ OUTPUT
Square wave input from
low-frequency oscillator 10 kQ
50 Hz, 10V p-p
Ws

Onkyo A-8870 Specifications

General

Frequency Response	5Hz-100kHz (+1dB, -3dB)
Power Output	80 W + 80 W (8 ohms, 20Hz-20kHz, THD 0.008%)
Total Harmonic Distortion	0.008%
Damping Factor	60 (8 ohms, 1kHz)
Input Sensitivity	2.5 mV (MM)
Speaker Load Impedance	4 ohms - 16 ohms
Dimensions	435 x 149 x 431 mm
Weight	21.5kg