Model 8904A Adjustments
NOTE
To
minimize ringing on the signal pulses, use low-capacitance, divide-by-ten
probes. Test points
A2TP6
and
TP7
are provided
for
convenient grounding
of
the
probes.
For
purposes of timing, consider
0.1
V
at
A2TPl
to be the threshold
of
a
logical
high.
For
the other testpoints, consider
1.3
Vdc to be
the
threshold
of
a logical high.
c. Connect
test
point A2TP5 to channel
B
of
the dc coupled oscilloscope using a divider probe.
3.
On the Multifunction Synthesizer, press
SHIFT
PRESET.
After the instrument presets, key in
SHIFT
SPECIAL
7
ENTER
f2
(Status)
ON
LAST
f2
(Status)
ON
f4
Adjusting
A2R105
4.
On
the Multifunction Synthesizer, adjust potentiometer
A2R105
for
a
high period
of
45 ns on
the
13
MHz (clock synchronization) signal displayed on channel B of the oscilloscope.
Adjusting
A2S2
5.
Connect channel
B
of the oscilloscope to A2TP2.
6. On the Multifunction Synthesizer, toggle the switches on array A2S2 one at a time until the
positive-going edge of channel
B
lines up with every other positive-going edge
of
channel
A.
(The frequency
of
channel
B
is one-half the frequency
of
A.)
NOTE
When
setting
the
delay switches, only one switch
in
an
array
should be closed
at
a
time; therefore, when changing switch settings open the currently closed
switch before closing
the
desired switch.
Set the switches to
the
settings that give the result nearest
the
desired
ualue.
Adjusting
A2S4
7.
Move the probe of channel
B
to test point A2TP5. Note the time delay between the positive-going
edges of the signals
on
channel
A
and channel
B.
Delay Between Signals
at
A2TP1 and A2TP5:
ns
8.
Subtract
35
ns from the delay measured in step
7.
(If the difference is negative, use
0.)
Computed Delay: ns
9.
Move the probe of channel B to
test
point A2TP4.
10.
On the Multifunction Synthesizer, toggle the switches on array
A2S4
one at
a
time until the
positive-going edges of the signal on channel B lag the positive-going edges on
A
by the delay
computed in step
8
to within
f7
ns.
Adjusting
A2S3
11.
Move the probe
of
channel B to test point A2TP3. Toggle the switches on array A2S3 one at a
time until the positive-going edge
of
channel
B
lags the positive-going edge
of
channel
A
by
48
to 62 ns.
Adjustment
7
5-15
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