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Section
V
Model
5254C
e.
Remove
the four
screws
that
secure
the
mixing
frequency
dial
and
remove
dial.
f.
Remove
the
two
screws
that
secure
front
panel
to
bottom
plate
(MP8).
g.
Cut connecting
wires
at
meter
terminals.
h.
Remove
panel
from
instrument
to
permit access
to
meter.
i.
Remove
the
two screws
from meter
bezel
at
sides
of
meter.
Push
bezel
forward
as far as possible.
j.
Grasp meter
and
gently pull (with
bracket
MP5)
backwards
out
of
front
panel
hole.
k.
Remove
meter
bracket
(MP5) and hardware
from
meter and
install in
identical
manner
on
replacement
meter.
l.
Replace
meter
(with
bracket)
in unit
by reversing
procedure used
in
steps a
through
k.
Strip
1/4 inch
insulation
from
ends
of
each
connecting wire and solder
to
meter
terminals.
White wire goes
to inside
term-
inal;
black wire goes
to
outside terminal.
5-36.
CIRCUIT
ADJUSTMENTS.
5-37.
MULTIPLIER AMPLIFIER ALIGNMENT PRO-
CEDURE.
Two
procedures are
given
for
multiplier
amplifier alignment;
Procedure
a
is to
be used
if
the
multiplier
is
working and
just
requires peaking,
and
Procedure b
if
the multiplier
has no
output
(checkout-
put
by
measuring
dc voltage
at
junction
of
C25
and
R16;
normal
reading
is 2
volts
or more).
a.
1)
With
counter
power
off,
connect converter
to
counter with Extension Cable
HP
10506
B.
2)
Remove
four
screws which
secure
MP6
(top
plate)
and
remove MP6.
3)
Set
UHF
Signal
Generator
to
any frequency
between
2
and
3
GHz
at 50
mV
and connect
to
converter
INPUT.
4)
Turn
counter
power
on
and
set
controls as
shown
in
Figure
3-1.
Tune
converter
for
a
maximum
indication
on Level
Indicator
Meter.
5)
Adjust
UHF
Signal
Generator
output level for
a
reading on
the
red/
green
line
of
the
con-
verter
Level
Indicator
Meter.
NOTE:
If
counter displays a difference fre-
quency below
1
MHz,
adjust
UHF
Signal
slightly
so counter display
is
between
1
to
50
MHz.
6)
Adjust
A1L2,
A1L3,
A1L5,
A1L6, A1L8,
A1L10
and
A1C25
for
a
maximum
indication
on Level
Indicator
Meter.
NOTE
:
If
the
Level
Indicator
Meter
reading
increases
to
above 1/2
of
full
scale,
readjust
the
UHF
Signal
Generator
to
keep
indication
near
the
red/'
green
line.
7)
Potentiometer
A1R17
needs no
adjusting
pro-
viding input sensitivity
is
between
25
mV
and
50
mV
throughout
the input
frequency
range.
8)
Replace
MP6
(top plate).
b.
1)
With
counter
power
off,
connect converter
to
counter with Extension Cable
HP
10506B.
2)
Remove
four
screws which
secure
MP6
(top
plate)
and
remove MP6.
3)
Turn
counter
power
on.
4)
Connect
HP
140
A
with
HP
14 10
A
plug
in
(1000
MHz
Oscilloscope),
using
an
HP
10214A
Divider and an
HP
102
17A
Blocking Capacitoi
to
collector
of
A1Q1.
Set
Oscilloscope
vert-
ical
gain
for
5V/cm(with
10:1
Divider
set to
.
5
V/cm)
and
horizontal
to
.
05
/is/
cm,
and
trigger oscilloscope
from
counter
OUTPUT
STD
FREQ
10
MHz
(rear
of
counter).
5)
Observe waveform
and
tune
A1L2
for
maxi-
mum.
Waveform
and amplitude
should ap-
proximate
that in test point
2,
Table
8-1.
6)
Connect
oscilloscope
probe
to
the collector
of
A1Q2.
Set
oscilloscope Vertical
to
2
V/cm.
7)
Observe waveform
and
adjust
A1 L3
for
maxi-
mum
;
then
adjust
A1L5
for
maximum. Wave-
form
and amplitude should approximate
that
in test
point
3,
Table
8-1.
8)
Connect
oscilloscope
probe
to
collector
of
A1Q3.
9)
Observe waveform
and
adjust
A1L6
for the
approximate
waveform
and amplitude shown
in test point
4,
Table
8-1.
10)
Connect
oscilloscope
probe
to collector
of
A1Q4.
Set
oscilloscope Vertical
to
1
V/cm.
11)
Observe waveform
and
adjust
A1L8
for
max-
imum.
Waveform
and amplitude
should ap-
proximate
that
shown
in test
point
5,
Table
8
-
1
.
12)
Connect
oscilloscope
probe
to
collector
of
A1Q5.
Set
oscilloscope Vertical
to
2
V/cm.
13)
Observe
waveform
and
adjust
A1
LI
0 for
max-
imum.
Waveform
and amplitude
should ap-
proximate
that
shown
in
test point
6,
Table
8
-
1
.
14)
Connect
oscilloscope
probe
to
collector
of
A1Q6.
Set
oscilloscope Vertical
to
10V/cm.
15)
Observe waveform and
tune
A1C25
for
max-
imum.
Note two
maxima
should be noted as
the capacitor
is
turned through
360°.
Wave-
form
and amplitude
should
now
approximate
that
in test
point
7,
Table
8-1.
The
output
should
be a
sine
wave
of
50
Me,
approximately
20
volts
amplitude;
if
not
proceed
to
steps 16
through 19 and then
repeat step
15.
16)
Adjust capacitor
A1C25
to the centei
of
its
range
(notch
perpendicular
to
axis
of leads).
17)
Unsolder
from
the
board
the
end
of
A1L12
at
its
junction
with
A1L11
and
A1C23.
18)
Observe
the
waveform
and
tune
A1L12
for
a
maximum
by increasing
or reducing the loop
diameter.
Resolder
A1L12
to the
board.
19)
See Para. 5-37
a for
final
peaking
adjustment.
5-4
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Table of Contents
Troubleshooting
