Fluke 6060B - Digital and Control Troubleshooting

maintenance
TROUBLESHOOTING
AND
REPAIR
4D-25. DIGITAL
AND CONTROL
TROUBLESHOOTING
If the
symptoms
indicate a
digital
or control
problem,
the
following
suggestions
may
help
you isolate the fault
to a particular
functional
circuit. In
this
manual,
refer to the
schematic diagrams
in Section
S, and refer
to
Section
3 for the Theory
of Operation.
First, verify
that all assemblies
arc receiving
the correct
voltages
from
the power
supply.
The
most
obvious symptom
of failure in
the
Controller
assembly
is a blank
front
panel. A
properly
operating front
panel indicates
that
most of the
Controller
circuitry is
functional.
If the front
panel is totally
blank or
unresponsive
to any
keystrokes,
the
microprocessor
kernel
should
be
checked
first.
See the
paragraphs
entitled
Microprocessor
Kernel
in
this section.
If
the
front panel is
operating
correctly
but the RF output
is incorrect,
determine if the
fault
is
on the Controller
side
of connector
PlOl
. The control
to most of the
audio and RF
analog
circuitry passes
through
PIOl via
buffers U15
and U16 on the
Controller PCB
A2A7.
4D-26. Control
Activity
This
can
be checked by
verifying
data activity
on the data
and address lines
of PIOI.
Program the
bright digit for
lOO-Hz resolution
in the FREQUENCY
display. While
pressing the EDIT
[+]
key, observe
with an oscilloscope
the activity
on PlOl. Pressing
one of the EDIT
keys
sends bursts
of frequency and
level control data
through the
buffers.
Although
it is difficult
to determine
if the data,
(BDO-7)
and address
(BABO-2)
signals
on
PIOI
are valid at any
given time,
the most
common
failures
seen at
this
point are
totally
inactive signals.
Between
bursts,
the data and
address
signals are
in
the high
impedance
state (tri-stated).
Be careful not
to
confuse
this high
impedance
state
with total
inactivity.
Observing these
signals
on a
known
good
unit may
be helpful.
If signals are
found
to be totally
inactive,
inspect
the buffer
control signals
on
U 1
5
(pin
1
),
and
U 1
6
(pins 1 and
1
9)
of the Controller,
A2A7. If
the
buffer control
signals are active,
check the
buffer inputs
that
correspond
to the inactive
outputs. If
the inputs show
activity,
replace the
buffer and again
check
the
signals.
If, however,
the inputs to the
buffers are also
inactive,
trace the
signals back
and determine
the fault location.
If all
data and address
signals
show activity
and
their
timing
roughly
corresponds
to the
select
signals
BSELOL.
and BSELIL,
assume
for now
that the
Controller
is
sending
the
correct data and
continue
on.
4D-27.
Latch
Control
Use the [SPCL]
[I][5] keys
to
check each
available
latch on the
RF circuit
boards to verify
that the
correct
data is
reaching
them.
Passing
this
test is a
good indication
that the
fault
is
not
m the Controller.
If the IEEE-488
option
is present,
and an
IEEE-488
Bus
Controller
is
available
additional
bit-level
control
of the
hardware
is available
by using
the
monitor
commands
(see Section
2). These
commands
allow
you to directly
program
the
DACs,
or read and
write data to
any desired
location.
4D-28.
Microprocessor
Kernel
Connect
an oscilloscope
probe to
the external
clock
input
of A2A7
UI pin
2. There
should be a
symmetrical
10-MHz
square
wave with
an adequate TTI.
logic
level. If the
4D-10