Sytm Peaking Assembly-Level Troubleshooting; Sytm Peaking Assembly-Level Troubleshooting; The Fault Annunciator Comes On - HP 8340B Manual

SYTM Peaking
Assembly-Level Troubleshooting
THE FAULT ANNUNCIATOR COMES ON
If
the
FAULT annunciator comes
on,
determine the
function that caused the fault as follows:
1.
Press
[INSTR PRESET] [SWEEPT1ME] [1] [SEC] [SHIFT] [MANUAL].
If
the peak or tracking indicator is flashing, the peaking routine
failed
to
find
a
peak
within the
range of the SYTM slope DAC. This can
be caused
by:
a.
The
A28 SYTM driver assembly may
not
be shifting
the
passband.
b.
There may
not be enough
power
from the
SYTM for
proper
ALC
operation.
c.
The A16 ALC modulator may
be defective.
If
the instrument won't auto track properly
(no fault indication), the problem may
be:
a.
The ALC loop
is not leveling.
b.
The ALC
loop
is
oscillating during leveling.
c.
The YO endpoints are off (lock and
roll
errors).
2.
Look at the
CMP
test
point
(A28TP3) for
an indication
of how the slope DAC
is
varying slope
compensation (see Figure H-4 for
a
typical CMP
waveform).
If
the waveform
is
incorrect, the
A28
assembly
is the most probable fault.
3.
Check the MODLVL test
point
(A26TP3). Refer
to
Figure H-5 for
a
typical
MODLVL
waveform.
4.
Check
the
MOD test point (A26TP3). See Figure H-6 for
a
typical MOD waveform.
If
either the
MODLVL or MOD signal
is
significantly different from Figures
H-5
and H-6, the most probable
cause
is
the A26 assembly.
5.
To
clear the fault annunciator, press [INSTR PRESET], or turn the
line
power
off
then on.
-1.00000
s
0.00000
s
1.00000
s
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y
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A
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p^
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^
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Ch
1
Timebase
100.0
mvolts,div
200
msfdiv
Offset
De
1
ay
250.0
muolts
- 0.
00000
s
Figure
H-4. Typical CMP Waveform
HP 8340B/41B
SYTM
Peaking Assembly-Level Troubleshooting H-19