Service Model
8901B
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 amount of time. In most instances they can
differentiate between an instrument hardware failure and a Controller
or
software problem. The checks
should be done in order.
(J1)
LineCheck
Procedure:
Remove instrument top cover (three screws) and switch POWER to ON.
Normal Indication:
1.
The fan runs indicating power is present on the power transformer secondaries.
2.
The five green LEDs on the
A10
Power Supply Regulators Assembly are lighted indicating
that the supplies are nominally operating.
If Indication Abnormal:
1.
Check the rear-panel line fuse and line voltage selector. Check Mains wiring. (See Service
2.
Check the individual regulators. (See Service Sheet BD5.)
Sheet
31.)
@
Power-Up Checks
Procedure:
If
there are any jumpers on the TEST
test
points on the
A13
Controller Assembly,
remove them. Switch POWER to STBY for five seconds and back to ON. Note the sequencing
of
the four
TEST
LEDs
on the top of the Controller Assembly as the instrument powers up.
Normal Indication:
The four TEST LEDs light in the following sequence:
1.
Indeterminate
for
about second.
2.
(
)
(
)
( )
(1)
for about
2
seconds. This indicates the start of the power-up routines and the
3.
(
)
(
)
(2)
(
)
for
about
1/4
second. This indicates the
start
of the power-up routines and the
4.
(
)
(4)
(
)
(
)
for
about
1/4
second. This indicates the running of the Local Oscillator Check.
5.
(8)
(4)
(2)
(1)
for
about
10
seconds. This indicates that all power-up checks passed
and
that
6.
(
)
(
)
( )
(l),
with
(1)
blinking indefinitely until a key
is
pressed. The behavior of the
LED
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:
run
of
the Read Only Memory Check.
run
of
the Random Access Memory Check.
a visual front-panel check can be made. (See
(J3)
below.)
(1)
is
also affected by the presence of an input signal.
Read Only Memory,
Random Access Memory,
Instrument Bus,
Local Oscillator (tuning only),
Keyboard (only that
no
key
is
down).
If Indication Abnormal:
If
the TEST
LEDs
come on and remain in the random state
of
step
1
above, unplug the
A14
Remote Interface Assembly and try again.
If
still faulty, check the
Controller Kernel. (See Service Sheet BD5.)
If
other indications appear in
or
after step
2
above, consult
Power-Up
Checks,
paragraph
8-9,
which discusses the individual checks, documents the error indications, and cross references to
the service sheets.
8D-12
Service Sheet
BDl
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