HP 8340b User Manual

A6
Keyboard
Interface
Assembly-Level
Troubleshooting
EQUIPMENT
REQUIRED
Oscilloscope
100
MHz
PROCEDURE
1.
Refer
to Figure G-6
and
remove
the
front
panel
assembly
from the
instrument.
2.
Disconnect
the
display
from
the
keyboard
and reattach
the
display
to
the
frame.
3.
Lay
the
keyboard down
in
front
of
the
instrument
to
allow
access
to
the
keyboard
interface.
One
Or
More
LEDS
Do Not
Light
When
[INSTR
PRESET]
is
Pressed
1.
The trouble
is
the
A6
annunciator
latches
or
the
A5/A7
assemblies.
None
of
the
Annunciators
Light
When
[INSTR
PRESET]
is
Pressed
1.
Troubleshoot
the
A6
instrument
preset
buffer
or
annunciator latches.
All
of the
Annunciators
Except
SWP
Remain
On
After
Power
Up
or
After
[INSTR PRESET]
1.
Troubleshoot
the
A6
address decoder
or
instrument
preset
buffer.
Check
LED
I
Or
II
Remain
On
After
[INSTR PRESET]
1.
The
instrument
processor
self
test has
failed.
Refer
to
the
A60
processor
assembly
troubleshoot¬
ing in
the
controller section
functional
group.
Pressing
a
Key
Gives
No
Response
(Display
Does
Not
Change
and
the
Instrument State Does
Not
Change)
1.
With
the
oscilloscope, probe
HI KEY
DN
SRQ
(A6
TP3),
at
5
ms/Div.
This
signal
should be
low.
When
you press
a
key,
it
should
go
high
for
a
period
of
time
that
is
equal
to the
instrument
microprocessor
SRQ
response
time.
This
varies
between
100
us
and
25
ms.
If
HI
KEY
DN
SRQ
is
correct,
the
trouble
is
the
SRQ
buffer.
If
HI
KEY
DN
SRQ
is
incorrect,
the
trouble
is
the
key down
timer.
Pressing
a
Key
Produces Several
of
the
Same
Characters
in
the
Display
1.
Probe
LOW KEY
DISABLE
(A6TP13).
This
signal
should
go
low and
remain
low
until
after
the
key
is
released.
If
LOW KEY
DISABLE
is
working,
the
trouble
is
the
key down
timer.
If
LOW KEY
DISABLE
is
always
high,
the
trouble
is
the
key
up
timer.
HP
8340B/41B
A6
Keyboard
Interface
Assembly-Level Troubleshooting
G-ll

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English