HP 8340b User Manual

A57
Marker/Bandcross
Assembly-Level
Troubleshooting
DIAGNOSTICS
The
SHIFT
M4
diagnostic
can
isolate
a
problem
to specific
circuitry
on
the
A57
assembly.
This
service
diagnostic
tests
DACs
and
control circuitry,
and isolates
the
problem to
individual
sections
of the
A57
assembly.
Table
F-1 lists
the
A57
assembly
circuitry
tested
by
the
SHIFT
M4
routines.
Refer
to
the
A60
processor
assembly
troubleshooting
section
for
full
details
on
the
SHIFT
M4
tests,
their
interdependence,
and
display
results.
Table
F-1.
Diagnostic
SHIFT
M4
Tests
—
A57
Assembly
Number Name
Description
16
20
Marker/RAM
RD/WR
Manual Sweep
DAC
Bandcross
DAC
Verifies
operation
of
the
address
register,
sweep
event
memory,
Read/Write
RAM
and
Read/Write
strobes
from the
A60
processor
assembly
Verifies
operation
of
the
manual
sweep
DAC.
Verifies
operation
of the
sweep
compantor
and
the
read status
buffer.
The
SHIFT M4
diagnostic
tests approximately
50%
of
the
A57
marker/bandcross
assembly circuitry.
ASSEMBLY
ISOLATION
To
help
verify
that
a
problem
is
on
the
A57
assembly, remove
the
assembly
and
observe
the
instru¬
ment.
With
the
A57
assembly
removed,
you
should
see
the
following:
1.
Following
power
on
or
instrument
preset,
observe
the
instrument
check
LEDs:
CHECK
II
should
stay
on,
and
CHECK
I
should
go
off.
2.
All
16
self
test
LEDs
on
the
A60
processor
assembly
should
remain
on.
3.
When
sweeping,
the
sweep
ramp
should
stop
at
12V
before
resetting.
NOTE:
Check the
sweep ramp
(VSWP)
at
A58
TP10.
Because
the
buffers
for
the
sweep
signal
are
on
the
A57
assembly
(which
you
have
removed),
you cannot
measure
the
sweep
at
either the front
or
rear
panel
connectors.
4.
The
instrument
should
work
properly
in
CW
or
manual
mode,
and
perform
normally, except
for
the
absence
of
sweep
output and
display blanking.
5.
In
multi-band
sweep,
bandcrossings
all
occur
when
the
sweep ramp
reaches
12V,
rather
than
the
correct
voltages,
because
the
sweep
comparator
DAC
circuitry
is
located
on
the
A57
assembly.
A57
Marker/Bandcross
Assembly-Level
Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English