Fisher BA-6000 - Adjustment of the Power Amp P.C. Board; Before Adjustment; Zero Balance Adjustment; Power Amp P.C. Board Layout

2
ADJUSTMENT
OF
THE
POWER
AMP
P.C.BOARD
a)
BEFORE
ADJUSTMENT
ZERO
BALANCE
ADJUSTMENT
1.
After
the
power
switch
is
turned
ON,
allow
a
few
e
Connect
DC
V.T.V.M.
to
the
speaker
output
minutes
before
making
adjustment,
to
be
sure
of
terminal
and
turn
the
volume
control
fully
to
the
the
most
stable
operation.
minimum
position.
Turn
VRO1,
02
under
the
above
condition
until
the
output
voltage
becomes
2.
Connect
dummy
load
resistors
(8
ohms)
to
the
OV.
;
SPEAKERS
terminals.
3.
Use
a
DC
V.T.V.M.
(input
impedance:
More
than
50k ohms/V).
POWER
AMP
PC.BOARD
LAYOUT
(TOP VIEW)
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020
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13
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EXPLANATION
OF
PROTECTIVE
CIRCUITS
*For
about
two
seconds
after
the
power
switch
is
*If
the
speaker
terminals
are
short-circuited
or
the
turned
on,
the
speakers
remain
silent
because
the
ventilation
holes
at
the
cabinet
top
are
blocked
power
muting
circuit
operates
during
this
time.
during
long
periods.
of
operation,
the
internal
temperature
may
rise
abnormally.
At
about
90
C,
the
thermal
sensor
(temperature
detection)
circuit
becomes
activated
and
will
interrupt
the
signal.
\f
the
cause
is
removed
and
the
internal
temperature
1S
back
to
normal,
the
unit
automatically
resets
itse!f
to
restore
normal
operation.
:
—10—