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JVC A-X55 - Amplifier Adjustment Procedures; 6-(1) Drive Amp. Center Voltage Adjustment; 6-(2) Power Amp. Idling Current Adjustment; Printed Circuit Board Assemblies and Parts Lists

JVC A-X55
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6.
Amplifier
Adjustment
Procedures
Drive
Amp.
(TXX-
373)
Center
Voltage
Adjustment
6-(1)
Drive
Amp.
Center
Voltage
Adjustment
1.
Before
turning
on
the
power,
set
the
semi-fixed
resistors
(R311
for
Left
channel
and
R312
for
Right
channel)
of
the
drive
amplifier
circuit
board
(TXX-373)
to
the
center
position.
.
Adjust
the
semi-fixed
resistors
(R311
and
R312)
so
that
the
voltage
at
the
following
test
points
of
the
power
amplifier
circuit
board
(TXX-374)
is
within
a
range
of
+10OmV
or
less
five
minutes
after
the
power
is
turned
on.
Left
channel:
Measure
the
voltage
between
test
point
@)
and
test
point
@®
(ground).
Right
channel:
Measure
the
voltage
between
test
point
and
test
point
@®
(ground).
The
measurements
can
also
be
performed
at
the
speaker
terminals
if
the
relay
is
operating
normally.
6-(2)
Power
Amp.
Idling
Current
Adjustment
1.
Before
turning
on
the
power,
turn
the
semi-fixed
resistors
(R521
for
Left
channel
and
R522
for
Right
A-X55
No,
2589
Power
Amp.
(TXX-374)
@ @
Right
Channel
Left
Channel
Right
Channel
Test
Point
©
@
(@)rs2i
Left
Channel
Idling
Current
Adjustment
Fig.
8
channel)
of
the
power
amplifier
circuit
board
fully
counterclockwise.
.
Adjust
the
semi-fixed
resistors
(R521
and
R522)
so
that-
the
voltage
at
the
following
test
points
of
the
power
amplifier
circuit
board
is
within
a
range
of
9MV
~
13mV
after
the
power
is
turned
on.
Left
channel:
Measure
the
voltage
between
test
point
@
(emitter
of
0523)
and
output
at
the
test
point
Right
channel:Measure
the
voltage
between
test
point
@)
(emitter
of
Q524)
and
output
at
the
test
point
.
Readjust
resistors
R521
and
R522
about
five
minutes
after
the
power
is
turned
on
(the
heat-sink
temperature
must
be
sufficiently
high)
so
that
the
voltage
at
the
test
points
becomes
11mV.
Confirm
that
the
voltage
does
not
vary
when
the
heat-sink
temperature
increases
fur-
ther.
Note:
Be
sure
to
perform
the
measurement
with
the
probes
and
cabinet
of
the
measuring
equipment
separated
from
the
grounding
terminals
of
A-X55
or
of
other
measuring
equipment.
=
6A
7.
Printed
Circuit
Board
Ass’y
and
Parts
List
7-(1)
TXX-376
Equalizer
Amp.
P.C.
Board
Ass‘y
_
TXX-376-4
>
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