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MAINTENANCE
7.8 TROUBLESHOOTING
7.8.1 Recommended
Test Equipment
The troubleshooting
information
contained in this section
is intended
for qualified
personnel
having
a basic
understanding
of analog and digital
circuitry.
The in-
dividual
should also be experienced
at using typical test
equipment as well as ordinary troubleshooting
procedures.
Success in troubleshooting
complex equipment
like the
Model 194 depends not only on the skill of the technician,
but also relies on the use of accurate, reliable test equip-
ment. Table 7-7 lists recommended
equipment
to be used
when troubleshooting
the Model 194.
The information
presented in this troubleshooting
section
has be written
to assist in isolating a defective circuit or
circuit section. Isolation of a specific component
is left to
the technician.
7.8.2
Self Test
Schematic diagrams,
component
layout drawings,
and
parts lists for the various circuit boards within
the instru-
ment are located at the end of Section 8.
During the power up cycle, the instrument will check nun\
internal components
including
RAM and ROM nwm<~ri
to make certain everything
is in working order. I)uring the
test procedure,
all front panel annunciators
and disph)
segments will turn on to allow you to check th'lt all arc
operating
properly.
If a self test error occurs, the instrument
will display an
appropriate
error message, as summarized
in %bic 7-8.
Table 7-7. Recommended
Troubleshooting
Equipment
Dual-trace 100MHz Oscilloscope
Tektronix;
2235
DC Calibrator
AC Calibrator
Message
SELF TESTING
ROM ERROR
RAM ERROR
SELF TESTING
A/D RAM ERR 1
AID RATE ERR 1
NOISY A/D 1
SELF TEST PASS
ENTER 1 IF OK
Use
DCV, ACV, resistance
checks.
Digital waveform checks, AC
signal tracing.
Accurate DC signal source.
Accurate AC signal source.
Table 7-8. Self Test Display Messages
Description
-
Mother board test in progress.
ROM failure
RAM failure
A/D board test in progress
RAM or indicated
A/D defective
Improper
rate on A/D
A/D is noisy
Unit passed all tests
Prompt for user input
Comments
All LEDs on during
test.
Message appears for failure only.
Message appears for failure only.
Testing A/D
Failure only
Failure only
Failure only
Enter I if no error, 0 if error
shown (unit locks up)
7-25
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