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5700A/5720A Series II Calibrator
Service Manual
5-6
2801 A11: 8255 Port a Wires
The diagnostics software writes and reads data to port A of the 8255 IC on the DAC
assembly. A failure indicates the DAC assembly (A11) is probably at fault.
2802 A11: 8255 Port B Data Bus
The diagnostics software reads port B of the 8255 IC on the DAC assembly. A failure
indicates the DAC assembly (A11) is probably at fault.
2803 A11: 8254 Status Words
The diagnostics software reads the status of the 82C54 IC on the DAC assembly. A
failure indicates the DAC assembly (A11) is probably at fault.
2804 A11: DAC Heaters Not Regulated
The instrument is dormant and the heater voltages (REF HEATER and DCAMP
HEATER) to the hybrid assemblies are measured to be 0.7V ±10% ±0.2V. A failure
indicates the DAC assembly (A11) is probably at fault.
2805 5700 Not Warmed Up
If a heated hybrid assembly in the instrument is detected to not be in regulation the
length of time since the last reset is checked. This fault occurs if the time is less than ten
minutes since a reset.
2806 A11: ADC Amp Output Noise
The instrument is dormant. The ± inputs of the DAC adc amplifier circuit are connected
to common and the adc then takes ten readings. This failure occurs if the difference
between the lowest value and highest value of the ten readings is greater than 500 µV. A
failure indicates the DAC assembly (A11) is probably at fault.
2807 A11: ADC Amp Output Offset
The instrument is dormant. The ±inputs of the DACs adc amplifier circuit are connected
to common and the adc then takes ten readings. This failure occurs if the average of the
ten readings is greater than 3 mV. A failure indicates the DAC assembly (A11) is
probably at fault.