HP 8340B Manual page 128

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R31TP1: CN 4530
MHz
M
and
N
Divide Numbers
=
24
Test Point Frequency
=
3.333333 MHz
Figure B-13. Signal
at A31TP1
15.
Measure the frequency
at A33J1 (the counter should still
be connected in the configuration
described
in
step
7). If
the frequency
is
unstable,
proceed to step
18. If
the
frequency is stable,
proceed
to
step 16.
NOTE: If
the frequency out of A33J1
is
unstable,
it is still possible to check the operation of the
M
Divider on the A31 assembly.
To do
this, you
will
need
a
synthesized source (LO) which can produce
a
376.000000 MHz
CW signal (for example, an HP 8340A,
8341A,
8340B or 8341
B). Set the
LO
for
376.000000 MHz, power level 3 dBm, and connect the DUT's
10
MHz
REF OUTPUT to
the LO's
EXTERNAL FREQUENCY STANDARD
input. Disconnect
A31W2 from A33J1 and connect the
source
to A31W2. With this input signal,
A31TP2
should measure
4 MHz
(with an
M
Divide
number of 24) and
the its amplitude should be similar to A31TP1.
16. Using
the frequency measured in
step 15 and the following formula, calculate the frequency which
should
appear
at A31TP2 (Note: the divisor of 6 in the following
formula
will
only
work when the
M
Divide Number
is
24):
FA31TP1=(400MHZ-Fs,epl5)/6
17.
Connect Channel
1
of the oscilloscope to A31TP2 and set
the oscilloscope's
TIME/DIV
as appro¬
priate for the frequency you calculated in
step
16.
Determine
if TP2
is
at the frequency calculated
in
step
16
and the amplitude is similar to A31TP1.
If the signal
at
TP2
is bad, replace
A31.
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CAUTION
j
In the
M/N Loop adjustment
procedure, you
will be connecting
a
DC
power supply
to TP1 (TUNE), located on the cover of the A33 M/N output
assembly.
It
is critical that
you do not apply
a
positive
voltage to this test
point. Application of
a
positive voltage may
damage
the tuning diodes
on
the A32 VCO. Ensure that you
only apply
a
negative voltage to
TP1.
HP 8340B/41B
M/N
Loop Assembly-Level Troubleshooting