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vlode]
654A
Model
654A
Section
V
adjusted
to
Tabl
e
5-5. Front
Pane
l Troubl
eshoot
in
g
(See
Paragraph
5-74)
MONITOR
t
MOST LlKEL Y TROUBLE AREAS
ACTION REQUIRED
er
su
pply
is
POINT INDICATIONS
~~
lion by
dis
load AI Pin
restored by
ry,
t
rouble-
(Oscillator,
Amplifier,
je Control
!r)
10
t
restored
circuitry,
Iy.
Refer
to
adjusted
to
step
10
to
ABC
ABC
ABC
ABC
ABC
ABC
ABC
Oscillator
circuit or
Power
Supplies
Multiple
troubles
I)
Counter Emitter
Follower
2)
Meter
circuits
Avera
ge
Detector
Multiple troubles
I) Counter
Emit ter Follower
2)
Attenuators (S4) and/or
Impedance
switch
(A4)
Counter
Emitter Follower
ALC
Loo
p
- conSisting of Buffer and
Balanced
Amplifiers.
Average
Det
ecto
r a nd ALC
circuits
Metering
circuits (and
Avera
ge
Detector)
Attenuators
(S4) and
/o
r Impedance
Switch
(A4)
Go toQ)on
troubleshooting tree.
1
)
Troub leshool
2) Go
to@on
troubleshooting
tree.
I)
Troubl
es
hoot
2) Check all
positi
ons
of
attenuators and
impedance
switch.
Troub
leshoot.
Go toeD
on troubleshooting
tree.
Go
to@on
troubl
eshooti ng
tree.
Check
all
posi tio
ns
of attenuator
and
impedance
switch.
"len
ts; also
OTHER
nd AICI5.
TROUBLES
1
Amplifier
the top of
In
co
rrect
('top' and
Oat ness or
level
J.
2).
)r
in
the
No
output
on
ly
at certain
freque
ncies
In tegrator
Am pli tude
Incorrect
p
of
the
frequency
ALC
Loop
- consisting of Buffer and
Balanced
Amplifiers, Average
Detector
and
ALC
circuits
Oscillator calibration
Oscillator calibration
Go
toeDon troubleshooting tree.
Calibrate
Calibrate
-
A2Q8 thru
tCOUNTER OUTPUT
A'"
0.1 V
rms
into 50 ohms;
A'"
intermittent
or no signal
of
the
654A
meter indication
B '" +1 dBm
or greate
r;
B'"
less than + I dBm
-
j
Amplifier
should
be
a
Front panel
output
connectors
C
'"
approximately 0.8V
rms
into
50
ohms:
C '" intermittent
o
r
no
signal
the top
of
5,
the
two
with each
n there
are
Je between
he
sig
nal at
to-peak.
If
\2R76
and
®
Check
the input signal to the
Impedance networks
A4
Pin I and
A4
Pin
2, this
should
be 3
+/- I V
peak-to-peak
when the
attenuators are set at
+IOdBm. If
the
signal
is
not
present,
try
aU
positions
of
the
attenuators and
the impedance
switch.
@
Check
the de volta
ge
at
the
collector of
A2Q25
which should be from
+6
to +8
volts.
Troubleshoot
the
Balanced Amplifier
,
A2QII
through A2Q23
and associated components.
[f
in
step
®
the
dc voltages were
incorrect
and
were
equal and
opposite
then the problem
is
probably
in
the
diffe
rential
amplifiers A2QII
through
A2Q16
.
If
the dc volt
ages
are incorrect
but
of
the
same polarity then the problem is
probably in the
feedback
amplifier
A2Q22. A2Q23
and
A2Q17.
If the
output
signal is
not
prese
nt on
A4
Pin
3
and
®
(in
the BAL
modes of the
IMPEDANCE
swi
tch)
A4 Pin
4 then check
the
resistive networks on the
A4
board. If
it
is present, check
the cables
to th
e
output connectors
J3
and
14.
5-21
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