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Section
VI
Paragraphs 6-11 to
6-18
6.I
I.
INSTRUMENT COYER REIIOYAL.
6-t2.
To
remove
top
or
bottom cover, unlock
two
quarter turn fasteners which secure cover to instru-
ment.
Then
slide cover
toward
rear
of instrument.
To replace cover, reverse procedure.
WARNING
Lt5/230 VAC
AND DC SUPPLY
WrRES ARE
EXPOSED
WHEN
EITHER
INSTRUMENT
COVER IS
REMOVED.
EXERCISE
CAUTION
DURING
TROUBLESHOOTING, ADJ
UST.
MENT,
OR RE
P
AIR.
REMOVE
POWER
FROM INSTRUMENT BEFORE
REMOVING
OR
REPLACING
COVERS
OR
A,SSEMBLIES.
6-t3.
ASSEmBLY IOCATION
6-14.
Top
and bottom
internal
views of the Counter
are
shown
in
Figures 6-4 and
G-5.
These figures
show
the location
of
the assemblies,
connectors,
chassis
parts
and
test points.
Table
6-3.
Assembly Designations
A1
INPUT
SWITCH ASSEMBLY
(SENSITTVIT9
A2
TIME BASE
SWITCH
ASSEMBLY
A3
FUNCTION
SWITCH
ASSEMBLY
A4
MODE SWITCH
ASSEMBLY
A5
OUTPUT
SWITCH ASSEMBLY
A6
RECTIFIER ASSEMBLY
A?
REGULATOR ASSEMBLY
A8
DECIMAL POINT ASSEMBLY
A9
MEASUREMENT UNITS
ASSEMBLY
A10-
A14
LOW FREQUENCY
DECIMAL
COUNTER
A15-
A.16
MEDIUM FREQUENCY DECIMAL
COIJNTER
A17
HIGH FREQUENCY
DECIMAL
COUNTER
A1B
HIGH FREQUENCY
READOUT
A19-
A20
INPUT AMPLIFIER
ASSEMBLIES
A2t
FIJNCTION CONTROL ASSEMBLY
l^22
GATE CONTROL ASSEMBLY
A23
SAMPLING CONTROL
ASSEMBLY
A24
CRYSTAL OVEN ASSEMBLY
425
OVEN CONTROL ASSEMBLY
A26
OSCILLATOR ASSEMBLY
M,7
MULTIPLIER
ASSEMBLY
A28
MEDIUM FREQUENCY DECADE
DTVIDER
A29,
A34
LOW FREQUENCY DECADE
DTVIDERS
A35
TIME
BASE
CONTROL
ASSEMBLY
Model 5245L
6-15.
PRINTED CIRCUIT COffTPONENT
REPLACEfiIENT.
6-16.
Component
lead holes
in
the
Model 5245L
cir-
cuit
boards
have
plated
walls to
ensure
good
electri-
cal
contact
between
conductors
on
the opposite
sides
of the
board.
To prevent
damage
to this plating
and
to the
replacement component, apply heat sparingly
and
work
carefully.
The
following replacement pro-
cedure
is
recommended.
a.
Remove
defective
component.
b.
Melt solder in
component
lead
holes.
Use clean
dry
soldering
iron to
remove excess
solder.
Clean
holes
with
toothpick or
wooden
splinter.
Do not
use
metal tool
for
cleaning as
this
may
damage
through-
hole plating.
c.
Bend
lead
of replacement
component
to
the
cor-
rect
shape and
insert
component
leads into
component
Iead
holes.
Using heat
and
solder sparingly, solder
leads
in
place.
Heat may
be
applied
to either
side of
board. A
heat
sink
(longnose
pliers,
commercial
heat-sink tweezers, etc) should be
used
when
replac-
ingtransistors
anddiodes
in order to preventconduc-
tion of
excessive heat from the soldering iron to
the
component.
d.
Through-hole plating breaks are indicated bythe
separation
from
the board
of the round conductor
pad
on
either side
of the
board.
To
repair breaks, press
conductor pads against
board
and
solder replacement
component
lead to conductor
pad on
both sides
of
the
board.
6.17.
ADJUSTffIENTS.
6.18.
REGULATOR ASSEMBLY
A?.
CAUTION
When
troubleshooting
or
adjusting the power
supply, do not
short
supplies
to
ground
or
to
each
other.
This
will
damage
the diodes
and
transistors.
a.
Set
linevoltage to normalvalue
(115
or
230Vac).
b.
Connect
dc voltmeter
(Table
6-2)
to buss wire
between A16(11) and A18(6).
c.
Voltmeter
should read +20 Vdc
+
0.
5
Vdc.
If
voltage
is
outside
this range,
adjust ATRl7
(figure
7
-7.
d.
Vary line
voltage
from
103
to
t27 Yac
(20?
to
255
Vac).
The +20
Vdc supply should not vary more
than
0.
5 Vdc.
e.
Check
aII supplyvoltages at
locations,
and
under
conditions
shown
in Table
6-4.
Note
Input sensitivity levels must be
rechecked
if
power supply voltages are readjusted.
6-2
02349-1
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