Crown PSA-2 Service Manual

crown
When
soldering
to
lugs
(as
on
potentiometers),
the
mechanical
wire
wrap
should
be
a
J
hook
with
correct
insulation
clearance
as
shown
in
Fig.
7.14.
Fig. 7.14 Soldering to a Lug
Turret
terminals
also
utilize
the
“J”
hook
(Fig.
7.15).
Concentrate
on
good
heat
transfer
to
the
terminal
first,
then
the
wire.
If
two
wires
are
to
be
soldered,
be
sure
of
good
solder
flow
to
all
three.
Fig. 7.15 Turret Terminal
Desoldering
In
order
to
replace
a
component
part,
it
is
often
necessary
to
remove
the old
part
by
means
of
desoldering.
Several
methods
are
available,
the
most
common
being
the
braided
bare
copper
method.
This
wire
braid
is
placed
on
the
lead(s)
of
the
component
to
be
removed
with
the
iron
placed
on
top
of
the
braided
wire.
This
allows
the
solder
to
heat
up
while
simultaneously
adhering
to
the
braid.
When
the
braided
wire
is
removed,
the
joint
should
be
clean.
(See
Fig.
7.16)
Fig. 7.16 Wire Braid Desoldering
Next,
use
points
of
small
diagonals
to
lift
ends
of
component
lead
wires
and
remove
the
part.
This
procedure
is
applicable
to
both
PC
board
desoldering
as
well
as
terminal
and
lug
desoldering.
Note:
Be
sure
that
lifting.
of
the
component
lead
does
not
also
lift
the
copper
foil
pad
from
the
board.
Occasionally
a
small
amount
of
iron
will
be
helpful.
Soldering is one of the most reliable methods of joining
electronic component parts and assemblies. When
properly used, it can be one of the most helpful tools in
service repair work.
7.4 Basic Troubleshooting
As is well known, time is an important factor in providing
efficient service repair. Therefore, several time-saving
troubleshooting
steps
are
listed
below.
These
hints
may
or may not already be implemented in your service work.
If not, you may wish to experiment with them in order to
help improve your efficiency. After all, time is money!
A. Establishing Problems
User
complaints
about
defective
operation
may
not
always
be
clear
or
simple.
Furthermore,
the
trouble
the
user
has
experienced
may
be
due
to
the
system
and
not
the
unit
itself.
If
possible,
talk
to
the
user
about
this
problem.
This
will
usually
be
simpler
than
trying
to
understand
written
complaints.
A
first
hand
account
of
the
problem
can
help
in:
1) Getting the problem to re-occur on the service
bench.
2)
Getting
an
understanding
of
the
probable
cause.
Some troubles will be obvious upon visual inspection.
When
the
trouble
(or
its
symptoms)
is
not
so
obvious
ask:
a) Exactly what was the problem; how was it
noticable?
b) How was the unit being used?
c) Has the system as a whole been carefully
examined for possible external problems?
d)
How
long
had
the
unit
been
operating
when
the
problem occurred? Was it heat related?
If the user is unavailable or unable to explain the trouble
the next step is a thorough visual inspection.
B. Visual Inspection
A
good
visual
inspection
may
often
save
hours
of
tedious
troubleshooting.
Make
a
habit
of
proceeding
in
an
orderly
manner
to
insure
that
no
vital
part
of
the
7-7

Crown PSA-2 Specifications

General

Brand	Crown
Model	PSA-2
Category	Amplifier
Language	English