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Section
V
Mode
l
654A
d. The
ac
voltmeter
indication
shoul
d be 0 .1 V rms
or
greater.
verifyin
g
an
output of at
least
0
.1
V rms
into
50 ohms
.
e.
If the limits
are
not
met
troub
leshoot the
instrument.
5-38.
ADJUSTMENT PROCEDURE.
5-39.
The foll
ow ing
is
a
co
mplete
calibration
proc edure
for
the Model
654A
Test Oscillator.
These
adjustme
nts
s.hould
be
perform ed
only
if it
has
been
determined
by
the
Performance Checks
that the
654
A is
not meeting
its
specification
s. Figure 5-
14
shows
the
loca
tion
of all
internal
adjustments.
5-40.
CALIBRATION PROCEDURE.
5-41.
To
remove the
top
or
bottolll cover,reillove
the two
reta ining scre
ws,
slide
the
cove
r about 1/2
inch
to
the
rear
and
lift
off. To rem
ove the
side
covers,
remove
the
two
retaining
screws and lift
off.
To
repla
ce
the
covers
,
reverse
the
procedure.
THE 654A
CONTAINS HIGH IMPEDANCE
,
HIGH FREQUENCY
CIRCUITS. CONTAMINATION OF
THE
SWITCHES
,
CIRCUIT
BOARDS OR TUNING
CAPACITOR
WILL
CAUSE
HIGH IMPEDANCE
LEAKAGE PATHS AND
SUBSEQUENT
DETERIORATION OF THE PERFORMANCE OF THE
INSTRUMENT. AVOID TOUCHING ANY OF THESE
CIRCUITS WITH
THE BARE FINGERS, AS
SKIN
OILS
ARE EXTREMELY
CONTAMINATING.
IF HANDLING IS NECESSARY, WEAR
CLEAN
COTTON OR RUBBER GLOVES
.
DO
NOT
USE A
PENCIL TO
TRACE CIRCUITS
IN THE
INSTRUTvlENT. GRAPHITE PENCIL LEAD IS AN EXTREMELY GOOD CONDUCTOR
AND AN
ACCIDENTALLY
INTRODUCED PATH
OF
THIS TYPE
IS
SOMETIMES
DI
FF
ICULT
TO
LOCAT
E.
TO
AVOID
SURFACE CONTAMINATION
OF A PRINTED
CIRCUIT
OR
SWITCH
,
CLEAN
WITH
A
WEAK
SOLUTION OF WARM WATER
AND
MILD DETERGENT AFTER REPAIR
RINSE
THOROUGHLY
WITH CLEAN WATER
AND
ALLOW IT
TO
DRY COMPLETELY BEFORE OPERATING. DO
NOT
APPLY ANY
COMMERCIAL
MOISTURE SEALING
SPRAY TO
THE
BOARDS:
APPLI CATION
OF
THESE
AGENTS
MAY
CAUSE
LEAKAGE PATHS
.
TOP VIEW
J
BOTTOM VIEW
A2
A2
R4
.'
,'
A
ZRJ
/
:
• A
2T
P2
A2C
I • A2TPI
o
Fjgure
5-14. Locatjon
of
Internal Adju stm
en
ts
5-1
2
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