HP 8340B Manual page 277

All
Numeric Displays are Blank
1.
Connect the
oscilloscope to the CLK test point
(A2TP6), and set
it
to
0.5 ns/div,
1
V/div (0V
=
center screen). The waveform displayed should be low for 2.5 to 3.0 (is, with levels between
+2V
and approximately
—
2.5V.
If this signal
is
not present, the trouble is the
NUM CLK on the A2
assembly.
2.
Troubleshoot
the A2 assembly.
Entry Display Is Blank
1.
Connect oscilloscope to
ALPHA CLK
(A2TP2), and set
it to 0.5 ^S/div, 1V/div
(OV=Center
screen).
The waveform displayed should be
TTL
low-going pulses, 0.3
nS
wide, with
a
period of
1.4 iis.
If
this signal is not present, the trouble
is
the alpha display clock control
in
the A3 assembly.
2.
Connect the oscilloscope to
DATA (A2TP1), set
as
in
step
1.
The waveform
display should
indi¬
cated
both high and
low signal levels
approximately
1.4 (is
wide.
If
the
DATA signal
is always
low,
all
LEDs in the
ENTRY display will be off. If this signal
is not present, the trouble
is the A3 assembly
alpha display
shift register.
t
3.
Troubleshoot the A2 assembly.
The Same Segment(s)
is Missing In
Each Numeric Digit
1.
Troubleshoot the A2 assembly.
The Same Column is Missing
in
Each ENTRY DISPLAY Character
1.
Troubleshoot
the A2 assembly.
One Entire Numeric Display
is Blank
1.
Troubleshoot
the A2 assembly.
The Display Goes
into
Self Test When the Instrument
is
Turned ON and
Does Not Respond to Normal Instrument Functions
1.
The
trouble
is the
A3
instrument bus interface.
HP 8340B/41B A3
Display
Processor
Assembly-Level Troubleshooting G-9