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2.8.3.9.1 Minimum Output Test
The coarse and fine control attenuators, A1 and A2, are set for minimum output and the voltage
output is measured. If the output exceeds a prescribed limit a FAIL message is displayed and the
attenuator circuitry needs corrective maintenance.
2.8.3.9.2 Attenuator Test
To produce a prescribed set of output values the unit increments and decrements internal
attenuators to check the linearity of the attenuators. A FAIL message indicates that the linearity of
the control DAC is suspect and corrective maintenance is required.
2.8.3.9.3 Sinewave Test
The sinewave generator output at 60 Hz is tested. The measured output must agree with a preset
value within a prescribed limit in order to pass the test. A FAIL message indicates that the
sinewave generation ROM and DAC circuitry is suspect and in need of corrective maintenance.
The high voltage amplifier is not used in this test.
2.8.4. HANDHELD UNIT TESTS
All of the Hand Held Unit controls are checked for correct operation in this test. The name of a
control key is displayed and the operator responds by pressing the indicated key. If the control
key operates correctly, the next key name is displayed; otherwise no action occurs and the test
'hangs' at this point. Corrective maintenance is required in the circuit area of the faulty key in
order for the test to proceed. The PASS message is displayed when all controls operate correctly.
Press the MODIFY DOWN key to return to the test menu after successful completion of the Hand
Held Unit test. The test can be terminated any time by pressing RESET.
2.8.4.1 DEBUG UTILITIES
This menu item contains a number of test functions, which allow the operator to view "raw"
measurement data items that are critical to the operation of the PMC. Facilitate amplifier
adjustments in the current and voltage measurement sections by observing the offset data while
adjusting the trimmer controls. In addition, amplitude control DACs can be set by the operator to
allow current and voltage outputs to be changed independent of processor feedback control. This
allows the repair technician to observe operation of individual hardware items at fixed settings
without interference due to processor control actions. Each voltage and current output range can
be individually exercised.
Upon entry into the test, the operator is queried by the display message CURRENT OR
VOLTAGE?
When the operator presses the CURRENT or VOLTAGE key, according to the series of tests
desired, the message ‘OFFSET TEST XXXXX’ appears. XXXXX is the ADC reading of the
output of the current or voltage measurement operational amplifier circuit with a zero input signal.
The ADC reading is nominally 300 +20 when the amplifier offset is properly adjusted. If the
reading does not agree the appropriate trimmer should be adjusted. Replacement of the
operational amplifier may be needed if the offset cannot be adjusted to the nominal value.
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