Model
8903B
Service
TROUBLESHOOTING
General
The troubleshooting checks that follow are a starting place for locating an instrument fault. They are easy to
perform and give much key information in a short time. In most instances they can differentiate between an
instrument hardware failure and
a
Controller or software problem. The comments associated with each procedure
summarize the information known as a result of passing
or
failing the check. The checks should be done in
order.
For
additional information on the troubleshooting philosophy used in these checks, refer
to
General
Roublesho
o
ting,
paragraph
8-
16.
Linecheck
Procedure:
Remove the instrument top cover (three screws) and switch LINE
to
ON.
Normal Indication:
The four green LEDs on the
A13
Power Supply
and
Motherboard Assembly are lighted
indicating that the supplies are nominally operating.
If Indication Abnormal:
Check rear panel line fuse and line voltage selector. Check Mains wiring. See Service
Sheet
20.
Check individual regulators. See Service Sheet
BD5.
(J2)
Power-Up Checks
Procedure:
If
there are any jumpers on the
TEST
test points on the
A8
Controller/Counter Assembly, remove
them. Switch LINE to
OFF
for five seconds then back to
ON.
Note
the sequencing of the four TEST LEDs on
the top of the Controller/Counter Assembly as the instrument powers up.
Normal Indication:
The four TEST LEDs light in the following sequence:
1.
Indeterminate for about 1/8 second.
2.
(
)(
)(
)(1)
for about second. This indicates the
start
of the power up routines and the run of the Read Only
3.
(8)(4)(2)(1)
for
about
2
seconds. This indicates
that
all power-up checks passed
and
that a visual front-panel
4.
(8)(4)(2)(1), with
(1)
blinking indefinitely until a key
is
pressed. The behavior
of
the LED
(1)
is
also affected
Memory Check.
check is in progress (see
@
1.
by the presence
of
an input signal.
Any other sequence indicates a failure of the check. Passing this check indicates that the Controller
is
functioning
properly and that there is no catastrophic failure in the following circuits:
Read Only Memory,
Random Access Memory,
Instrument Bus, and
Keyboard (only that no key is down).
If
Indication Abnormal:
If
the TEST LEDs come on and remain in the indeterminate state of step
1,
check the
Controller Kernel. See Service Sheet BD4.
If
other indications appear in
or
after step 2, consult
Power-
Up
Check,
paragraph
8-27,
which discusses the individual checks, documents the error indications, and cross references to
the service sheets.
(J3)
Front-Panel
LED
Check
Procedure:
Disconnect all connections to the INPUT. Switch LINE
to
OFF
and back to
ON.
Normal Indications:
After less than
1/8
second, all front-panel LEDs, display segments and decimal points
should light for about three seconds, then the displays blank for one second then after a few seconds settle to
readings of
0.000
kHz in the left display and <0.100 mV in the right display. The measurement cycle indicator
LED in the upper left-hand corner
of
the right display should blink rapidly. The kHz and mV annunciators and
the AC LEVEL and
80
kHz LOW
PASS
key lights should be on. This indicates that the Controller
is
able to
output to the front-panel LED and display latches which are all operative.
rev.20JUN87
8A-7
To Next Page
Loading...
