HP 8340B Manual page 187

9.
Is the
YO Frequency Change Porportional to YO TUNE?
Record the
actual
YO frequency.
Disconnect
YO TUNE and FM COIL DRIVE, cables A49J1 and
A49J2. Place
a
50^1 load on the YO
TUNE
cable,
A49J2. (These cables
will remain disconnected
for the remainder of the troubleshooting.)
Note the
YO frequency
now and
compare
it with the value recorded before the cables
were
removed.
It
should have changed
10
MHz
or less.
The YO
frequency
sensitivity
to YO TUNE
is
approximately
—3.0
MHz/V.
If
the frequency does
not change, or
if it
changes by more than
10
MHz,
this indicates
a
problem on the
ASS YO driver.
If
the
frequency change
is
proportional to the
YO TUNE
voltage, proceed to the next step.
10. Is
the Open-Loop YO Frequency Accuracy
±
5 MHz at 2.300 and 6.999 GHz?
With the YO TUNE and FM COIL cables
disconnected (and
a
50^
load on the
YO TUNE
cable,
A49J2), the YO frequency accuracy should be
within
a
±5
MHz
window over the entire YO
operating range.
The YO
accuracy should be checked at 2.300 and 6.999 GHz.
If the actual YO
frequency
is outside of these
limits, go to step
17; if
not, proceed to step
11.
11.
Is
Sampler
IF
Frequency and Power Correct?
Check for the correct frequency and power for the
SAMPLER
IF.
The frequency accuracy (open
loop) should be
±5
MHz,
the same as the YO.
If
the
SAMPLER IF
frequency and power are
correct, suspect the A49 YO loop phase detector;
if
not correct, proceed to question
12.
12. Is
RF Power into the A48 YO Loop Sampler Correct?
Check the
RF
signal
power
into the
A48 YO
loop sampler.
If the RF power
is correct, troubleshoot
the
A48 YO
loop sampler.
If
no signal
is present or
if
the
power
is incorrect, proceed to question
13.
13. Is
Directional Coupler Power Output at A45J2 Correct?
Check the coupled-back RF power out of the A45 directional coupler
at A45J2.
If
no signal
is
present or the power level is
incorrect, replace the A45
directional
coupler.
If the RF power
is
correct,
check the
AT215 dB attenuator, the A46 7
GHz
low pass
filter,
and connecting cables.
14.
Is
Directional Coupler Power Output at A45J3 Correct?
This portion of the troubleshooting guide
is
a
branch from question 2.
Check the RF power out of the A45 directional coupler at
A45J3.
If
the signal
is
present at the
correct power (Refer to Figure D-6, 2
of 2), then
a problem also exists
in
the main
RF path
(RF
Section).
To continue to troubleshoot the YO UNLK, however, go to question
3.
If no signal
is
present or
if
the power output
is low, proceed to question 15.
15.
Is
YO Power Output Correct?
Check
the
RF power
out of the YO. If
the
power
is correct (Refer
to Figure D-6,
2
of
2), trou¬
bleshoot the A45 directional coupler. If
no signal
is
present or
if
the
power is
low, proceed to
question
16.
HP 8340B/41B
YO
Loop Assembly-Level Troubleshooting
D-17