HP 8340b User Manual

A3
Display
Processor
Assembly-Level
Troubleshooting
EQUIPMENT
REQUIRED
Oscilloscope
100
MHz
PROCEDURE
1.
Connect
the
oscilloscope ground
to GROUND
(TP10)
and check
the
-5.2V
(TP11).
+5.2V(TP13)
and
4-12V
(TP14)
supplies
for
proper
voltages.
2.
If
the
supplies
are
correct,
refer
to
Figure
G-4
and
remove
the
front
panel,
separate
the
display
assembly from
the
keyboard,
and
reattach
the
keyboard
to
the
frame.
3.
Remove
eight
screws
from
the display
assembly
that
hold
the
A3
display
processor.
Turn
the
display
processor
over
and
reinsert
the
other
end
of
P1
through
P5
into
the
same
sockets
they
came
out
of.
Install
two
screws
to
hold
it
in
place.
4.
To
place
the
display
into
the
self-test
mode,
press
[SHIFT] [FREE
RUN].
Display
RAM
Test
Fails
1.
Replace A3U1.
Display
Checksum
is
Not
Equal
to
3A
1.
The
display
checksum is shown
in
the
ENTRY
display
during
the
front
panel
diagnostics.
Press
[SHIFT]
[FREE
RUN]
and
determine
if
the
checksum
is
equal
to
3A.
If
not,
replace
A3U1.
Numeric
And
ENTRY
Displays
Are
Dim
1.
Using
an oscilloscope,
check
the
display
supply
voltage
(A3P5
pin
1,2).
This
voltage
should be
4.0V
with 430
Hz
0.6V
P-P
ripple.
If
this
voltage
is
low
(<
3.2V),
the
displays
are
likely
to be dim;
if
this
voltage
is
less than
about
2.0V
the
displays
will
be
blank.
If
this
voltage
is
not
correct,
the
trouble
is
in
the
A3 display
supply.
Both
Numeric
and
ENTRY
Displays
are
Blank
1.
Check
LRESET
(A3TP12)
and
CLR
(A3P1
pin
1).
If
either
is
low,
the trouble
is
in
the
A3
preset
circuitry.
2.
Using
an oscilloscope,
check
the
display
supply voltage
(A3P5
pin
1).
This
voltage
should
be
4.0V
with
430
Hz
0.6V
P-P
ripple.
If
this
voltage
is
low
(<
3.2V),
the
displays
are
likely
to
be
dim;
if
this
voltage
Is
less than
2.0V
the
displays
will
be
blank.
If
this
voltage
is
not
correct,
the
trouble
is
in
the
A3
display
supply.
3.
If
both LRESET
and
CLR
are
high, and
the
display
supply voltage
is
4.0V or
greater,
proceed
to
All
Numeric
Displays
are
Blank,
and
ENTRY
Display
is Blank
troubleshooting
procedures.
G-8
A3
Display
Processor
Assembly-Level Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English