HP 8340B Manual page 280

Sometimes Keystrokes are Missed
by
the Instrument
1.
The problem
is in
the A6 key down timer.
The instrument Responds Only to Keystrokes and/or the Front Panel Knob
when
in
a
Swept Mode
1.
The
problem
is in
the A6
SRQ
buffer.
No
Response
when the Front Panel Knob is
Turned
1.
Press
a
function key and verify
that the ENTRY ON LED
lights.
If
this
LED does
not
light, the
trouble
is the annunciator latches.
2.
If the ENTRY
ON LED
is
on, probe CLK (A6TP1) with an oscilloscope set to 5
ms/Div. You
should
see
low going pulses as you turn the front panel knob, and the pulse width should vary with the
speed of rotation.
If CLK
is bad, the trouble
is in
the
RPG (rotary
pulse generator) or the
RPG
counters/data buffers.
3.
Probe
HI
RPG SRQ
(A6TP8). You should
find high going pulses
that vary in width depending on
the response time of the instrument processor to
an
SRQ. These
pulses should be between 100
US
and
25
ms.
If
HI
RPG SRQ
is correct, the trouble is the
SRQ buffer or the RPG counters/data
buffers.
If HI RPG SRQ
is not correct, the trouble
is
the
RPG count window timer.
Turning
the
RPG Causes Either
Very Small
or
Very Large Changes
in the
Active Function in
the ENTRY DISPLAY
1.
The
problem
is in
the A6 RPG count window timer.
The Instrument Does Not Preset when [INSTR PRESET]
is Pressed
1.
The problem Is in
the
A6 instrument preset
buffer.
G-12
A6 Keyboard
Interface Assembly-Level Troubleshooting
HP 8340B/41B