Racal Instruments 9901 Maintenance Manual page 65

DISMANTLING
Removal
of
Display
PCB
5.21 To change
a
component
such
as
an
LED
indicator
it is
necessary to
detach the
Display
Assembly from the
front
panel, but
complete removal should
be avoided
if
possible
because of the
numerous connections to the
main p.c.b.
(1)
Disconnect power.
Remove
covers (para. 5.1).
(2)
Remove
the carrying
handle
as follows:
-
(a)
Insert
a suitable tool
such
as
a
flat
bladed screwdriver into the
slot
in
the boss of
each
carrying
handle and
prise off
the cap, thus
exposing the retaining screws.
(b)
Extract the screws
which
hold the carrying
handle
to the
main
frame,
and remove
the
handle.
(3)
With
the
handle
removed
slide
back the short length of coloured metal
strip
into the
space normally occupied by
the
handle
boss. This will
allow
access
to
the screws
which
secure the
front
panel
to the
main
frame.
Remove
these
screws
.
(4)
The
front
panel assembly can
now
be carefully
withdrawn
as far as
the
wiring permits.
Take
care not to
damage
the flexible wiring
connector
to
the
main p.c.b.
when
withdrawing and
re-fitting.
(5)
To detach the Display Assembly:
-
(a)
(b)
(c)
(d)
5-12
Remove
the
knob from the
SENSITIVITY
control.
Unsolder
the earth connection
and input capacitor
connection
at the
'B'
input socket,
and
the
START/STOP
switch connection.
Remove
the four Pozidriv screws
which secure the
p.c.b.
to
the
front
panel
.
The p.c.b. can
now be detached
from the panel
.
For
complete removal,
unsolder the connections
to
the
main p.c.b.,
noting the colour coding.
9901 Vol .2