Fluke 5720A service manual 3103 A14 8255 Port C Fault, 3104 A15 HV Oven Regulation Fault

5700A/5720A Series II Calibrator

Service Manual

3103 A14: 8255 Port C Fault

The diagnostics software reads port C of the 8255 IC on the High Voltage Control assembly. A failure indicates the High Voltage Control assembly (A14) is probably at fault.

3104 A15: HV Oven Regulation Fault

The heater voltage of the High Voltage/High Current assembly HR7 hybrid is divided by 11 and is measured by the adc circuit. The heater voltage should be 0.7V ±10% ±0.2V. If it is out of tolerance, the High Voltage/High Current assembly (A15) is probably at fault.

3105 A15: HV I Oven Regulation Fault

The heater voltage of the High Voltage/High Current assembly H4 hybrid is routed to the High Voltage Control assembly via HV MUX0. The High Voltage Control connects HV MUX0 to the SDL which is routed to the DAC assembly where it is measured by the adc circuit to be 0.7V ±10% ±0.2V. A failure indicates the High Voltage/High Current assembly (A15) is probably at fault.

3106 A15: DC HV Amp Noise Fault

The High Voltage assemblies are configured in the dormant state with the exception that the DAC output, set to 0.0V, is connected to the DC HV AMPLIFIER/AC SENSE BUFFER circuit of the High Voltage/High Current assembly. This circuit is configured as an amplifier with a gain of 100 whose output is connected to the RCL line. The RCL line is routed to the DAC assembly where it is measured by the adc circuit. The adc circuit takes ten readings and this failure occurs if the difference between the lowest value and highest value of the ten readings is over 0.001V. A failure indicates the High Voltage/High Current assembly (A15) is probably at fault.

3107 A15: DC HV Amp Offset Fault

The High Voltage assemblies are configured in the dormant state with the exception that the DAC output, set to 0.0V, is connected to the DC HV AMPLIFIER/AC SENSE BUFFER circuit of the High Voltage/High Current assembly. This circuit is configured as an amplifier with a gain of 100 whose output is connected to the RCL line. The RCL line is routed to the DAC assembly where it is measured by the adc circuit. The adc circuit takes ten readings and this failure occurs if the average value is over 0.003V. A failure indicates the High Voltage/High Current assembly (A15) is probably at fault.

3108 A15: DC HV Amp Gain Fault

The High Voltage assemblies are configured in the dormant state with the exception that the DAC output, set to -0.001V, is connected to the DC HV AMPLIFIER/AC SENSE BUFFER circuit of the High Voltage/High Current assembly. This circuit is configured as an amplifier with a gain of -100 resulting in 0.1V at the output which is connected to the RCL line. The RCL line is routed to the DAC assembly where it is measured by the adc circuit. The gain of this circuit is determined by this reading along with the previously checked offset. This failure occurs if the determined gain is over 6% of the nominal -100. A failure indicates the High Voltage/High Current assembly (A15) is probably at fault.

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