Fluke 5720A 2801 A11 8255 Port a Wires, 2802 A11 8255 Port B Data Bus, 2803 A11 8254 Status Words

5700A/5720A Series II Calibrator

Service Manual

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.

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