46
~
HEATHKIT
~
IMGiH§i-M
GENERAL
PRECAUTIONS FOR BENCH TESTING
HOW TO TROUBLESHOOT YOUR
AMPLIFIER
1.
2.
Be
cautious
when
testing
solid-state
circuits.
Although
transistors
and
integrated
circuits
have
almost
un-
If
you
know
which
area your trouble
is
in,
apply the "Visual
Checks"
to
that
area.
limited
life
when
used
properly, they
You
may
also
go
directly
to the Trouble-
are
much
more
vulnerable to
damage
shooting Charts to see
if
the
difficulty
from
excessive voltage
or
current
you
are having
is
listed
in
one
of
the
then valves. A valve
can
often
be
"Condition" columns.
If
your
difficulty
operated under shorted,_zero-biaS,
is
listed
there,
check
the "Possible
excessive-voltage, or hi~h-curren~ causes"
listed
for
that
item
and
apply
conditions
for
short
periods of time the Visual Tests
listed
to the
Area
of
without
materially
damagin~
~he
valve. '
Difficulty.
Any
one
of these
same
conditions
can
completely destroy a
transistor
or
integrated
circuit
instantly.
Be
sure
you
do
not
short
any
terminals to
ground
when
making
voltage measurements.
If
the
probe
should
slip,
for
example
and
short
out a bias
or
voltage supply
point,
it
is
almost
certain
to cause
damage
to
one
or
more
transistors
or
diodes.
If
you
cannot resolve your problem with
the Troubleshooting Charts,
refer
to
the
"Stage-by-Stage Signal Injection"
tests,
beginning
on
Page
48.
Perform these
tests
as
directed.
First,
they will lead
you
to the area your trouble
is
in.
When
you
have
localised
your trouble
down
to
one
area,
check
the Possible Causes
listed
for
that
area.
3.
Do
not
remove
transistors
or
integrated
circuits
while the
Amplifier
is
turned on, since
this
could
damage
the Amplifier.
REPAIRtNG THE AMPLIFIER
When
you
make
repairs to your Amplifier
make
sure
you
eliminate the cause
as
well
as
the
effect
of
the
difficulty.
If,
for
example,
you
should find a
damaged
resistor,
be
sure
you
find out
what
it
was
(wiring
error,
etc.)
that
caused the
resistor
to
become
damaged.
If
the cause
is
not eliminated, the replacement
resistor
may
also
become
damaged
when_
the Amplifier
is
put
back
into operation.
CAUTION:
The
full
AC
line
voltage
is
preaent
at
several
points
(fuaeholder,
AC
outlets,
On-Off
switch,
etc.)
in
the
power
supply
circuit
of
th
e
Amplifier.
Be
careful
to
avoid
personal
shock
when
performing
the
checks
described.
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