A6 Keyboard Interface Assembly-Level Troubleshooting; A6 Keyboard Interface Assembly-Level Troubleshooting; Equipment Required; Procedure - HP 8340B 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