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H 52005-301D
4.
The
fuse holders are
accessible
at the
rear of the oscillators
The holder for
FSl
and FS3 marked
250
mA
-
115
V
and
100
mA
-
230
V;
the
marked voltages are representa-
tive
of'the
overall ranges
90
V
to
1
30
V
and
190
V
to 260
V,
for
which 250
m
A
and
1
00 mA
fuses should be fitted respectively.
The holder
of
FS2 is marked
250
mA HT.
5.
Replacement fuse
links
should be 20
mm
x
5
mm
cartridges of
the low
breaking
capacity
type (in a ccordance with Sheet
II
of
International Electrotechnical
Commission
Publication 127).
ACCESS
TO
COMPONENTS
6.
To
remove
the
case,
proceed as
follows
·-
(1)
Withdraw
the
coin-slotted
screws
from the
rear
of the instrument
and remo
ve
the
rear
cover
.
(2)
Slide the
assembly
of
the
three
units
and
the
bezel
forward from the
case.
To
separate the
three
units,
withdraw the screws attaching
them to the bezel.
Opening
the
oscillator chassis
7
.
The
chassis consists of the front panel
a
nd
three other sections hinged
to
it.
The four
sections are
normally arranged in the form
of a
rectangle when
viewed
from
above,
.
and
are
held
in this position by
screws.
The four sections
can
be hinged open
as
follows
(Fig.
1)
:-
(1)
Underneath, near the
rear, slacken
the
two
6
BA screws
in
slots, one
at
each
side of
the web
that spans the
chassis.
(2)
Slacken
the two
relatively
large
screws
at the
left-hand
side of
iO
'8
Ci
~T
OUT
51(;
OUT
""'
....
TM6S40A
•
VT4
1NI531
the rear
section
until
the shoulders
under the heads
of the
screws are
clear
of
the
slots through which the
screws pass.
It
should then be
possible
to separate the chassis
at
this corner, so
that the
sections
can
be hinged open.
Fig. 1
Opening
the oscillator
chassis.
8.
A
printed board is framed in
each of the
two longer sections
of the
c
hassi
s.
The wiring
sides are
facing
outwards
.
Each
board is held
in its frame by plastic clips.
Press these to
r
e lease
the
board,
ha
ving
disconnected
s
uch
leads
a
s
necessary.
Opening the
monitored attenuator
chassis
9.
The chassis
consists
of the step attenuator box
at
the
bottom,
the input
voltmeter box
behind
the
voltmeter
r
a nge switch
and the
matching transformer
box
on the
oth
er side.
10.
The
components
of
the
step attenuator can be examined
a
nd
limited
access can be
ob-
tained
by removing
the
bottom
cover of
the
step
attenuator box.
To
do
this,
withdraw the
ten
6
BA screws that hold
it.
To remove
the
step attenuator
box
completely, proceed as follows
·-
(1) Remove the bottom cover of the box as described
above
.
(2)
Remove
the
bar at
the back
of
the unit by withdrawing
the
two
4
BA
countersunk
screws
in
the
bar.
Chap
.
5
Page 2
Nov.
79
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