Fluke 5720A 3341 A9/A10 190 Ohm Cal Diag Fault, 3400 A12 8255 Control Word, 3401 A12 8255 Port A

Troubleshooting 5

Interpreting Diagnostic Fault Codes

assembly. The resulting 0.2V across the 10 kΩ portion of Z5 is connected to the +input of the differential amplifier. The output of the differential amplifier is routed to the adc circuit on the DAC assembly, via the RCL line, and measured for 0V ±3% ±15 mV. A failure indicates the calibration of the 100Ω resistance on the Ohms Main assembly (A10) is probably at fault.

3341 A9/A10: 190 Ohm Cal Diag Fault

The 2/5/10V SOURCE circuit is set for 2V and connected across the 1.9 kΩ string on the Ohms Main assembly. The resulting 0.2V across the 190Ω portion is connected to the - input of the Differential Amplifier on the Ohms Cal assembly. The output of the DAC assembly is set to 2V and connected across the 100 kΩ resistance in Z5 on the Ohms Cal assembly. The resulting 0.2V across the 10 kΩ portion of Z5 is connected to the +input of the differential amplifier. The output of the differential amplifier is routed to the adc circuit on the DAC assembly, via the RCL line, and measured for 0V ±3% ±15 mV. A failure indicates the calibration of the 190Ω resistance on the Ohms Main assembly (A10) is probably at fault.

3400 A12: 8255 Control Word

The diagnostics software reads the control word of the 8255 IC on the Oscillator Control assembly. A failure indicates the Oscillator Control assembly (A12) is probably at fault.

3401 A12: 8255 Port A

The diagnostics software writes and reads data to port A of the 8255 IC on the Oscillator Control assembly. A failure indicates the Oscillator Control assembly (A12) is probably at fault.

3402 A12: 8255 Port B

The diagnostics software reads port B of the 8255 IC on the Oscillator Control assembly during the instruments dormant state. A failure indicates the Oscillator Control assembly (A12) is probably at fault.

3403 A12: 8255 Port C

The diagnostics software reads port C of the 8255 IC on the Oscillator Control assembly during the instruments dormant state. A failure indicates the Oscillator Control assembly (A12) is probably at fault.

3404 A13: 8255 Control Word

The diagnostics software reads the control word of the 8255 IC on the Oscillator Output assembly. A failure indicates the Oscillator Output assembly (A13) is probably at fault.

3405 A13: 8255 Port A

The diagnostics software writes and reads data to port A of the 8255 IC on the Oscillator Output assembly. A failure indicates the Oscillator Output assembly (A13) is probably at fault.

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