Fluke 5720A service manual 3315 A9/A10 10 Ohm Cal Diag Fault, 3316 A9/A10 19 Ohm Cal Diag Fault

Troubleshooting 5

Interpreting Diagnostic Fault Codes

3315 A9/A10: 10 Ohm Cal Diag Fault

The 2/5/10V SOURCE circuit is set for 2V and connected across the 100Ω string on the Ohms Main assembly. The resulting 0.2 V across the 10Ω 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. Verify that the divided DAC voltage of 0.2V ±5% is at the +input of the Diff Amp by connecting DMM hi to TP20 and low to TP10 of the Ohms Cal assembly. If this measured voltage is out of tolerance, the Ohms Cal assembly (A9) is probably at fault.

3316 A9/A10: 19 Ohm Cal Diag Fault

The 2/5/10V SOURCE circuit is set for 2V and connected across the 190Ω string on the Ohms Main assembly. The resulting 0.2V across the 10Ω 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 19Ω resistance on the Ohms Main assembly (A10) is probably at fault.

3317 A9/A10: 100 Kilohm Ratio Fault

The 2/5/10V SOURCE circuit on the Ohms Cal assembly is set to 10V which is routed to the Ohms Main assembly and connected to the 100 kΩ string. The resulting 1V across the 10 kΩ portion is measured for 1V ±3% ±15 mV. A failure indicated the Ohms Main assembly (A10) is probably at fault.

3318 A9/A10: 190 Kilohm Ratio Fault

The 2/5/10V SOURCE circuit on the Ohms Cal assembly is set to 10V which is routed to the Ohms Main assembly and connected to the 190 kΩ string. The resulting 1V across the 19 kΩ portion is measured for 1V ±3% ±15 mV. A failure indicated the Ohms Main assembly (A10) is probably at fault.

3319 A9/A10: 1M Ohm Ratio Fault

The 2/5/10V SOURCE circuit on the Ohms Cal assembly is set to 10V which is routed to the Ohms Main assembly and connected to the 1 MΩ string. The resulting 1V across the 100 kΩ portion is measured for 1V ±3% ±15 mV. Measure the 1 volt across the 100 k Ω string by connecting a DMM hi to TP14 and low to TP2 of the Ohms Cal assembly (A9). If the voltage is out of tolerance, the Ohms Main assembly (A10) is probably at fault. If the voltage is within tolerance, the Ohms Cal assembly (A9) if probably at fault.

3320 A9/A10: 1.9M Ohm Ratio Fault

The 2/5/10V SOURCE circuit on the Ohms Cal assembly is set to 10V which is routed to the Ohms Main assembly and connected to the 1.9 MΩ string. The resulting 1V across the 190 kΩ portion is measured for 1V ±3% ±15 mV. A failure indicated the Ohms Main assembly (A10) is probably at fault.

5-19