Fluke 5720A 3916 A5 20DB Output Attenuation Fault, 3917 A5 30DB Output Attenuation Fault, Spare

Troubleshooting 5

Interpreting Diagnostic Fault Codes

3916 A5: 20DB Output Attenuation Fault

The 6.5V reference (BRF6, BSRF6) is connected to the Unity Gain Amplifier circuit on the Wideband Output assembly which drives the output through the Attenuators. The Wideband Output assembly is set for 20 dB attenuation so the 6.5V input results in a 0.325V output into 50Ω. This 0.325V is connected to the RCL line which is routed to the +input of the adc circuit on the DAC assembly. The DAC assembly output is connected to the -input of the adc circuit and adjusted until a null is achieved. This determines the exact value of the Wideband output. This fault occurs if the determined Wideband output is over 6% ±1.0 mV. A failure indicates the Wideband Output (A5) assembly is probably at fault.

3917 A5: 30DB Output Attenuation Fault

The 6.5V reference (BRF6, BSRF6) is connected to the Unity Gain Amplifier circuit on the Wideband Output assembly which drives the output through the Attenuators. The Wideband Output assembly is set for 30 dB attenuation so the 6.5V input results in a 0.103V output into 50Ω. This 0.103V is connected to the RCL line which is routed to the +input of the adc circuit on the DAC assembly. The DAC assembly output is connected to the -input of the adc circuit and adjusted until a null is achieved. This determines the exact value of the Wideband output. This fault occurs if the determined Wideband output is over 6% ±1.0 mV. A failure indicates the Wideband Output (A5) assembly is probably at fault.

3918 A5: 40DB Output Attenuation Fault

The 6.5V reference (BRF6, BSRF6) is connected to the Unity Gain Amplifier circuit on the Wideband Output assembly which drives the output through the Attenuators. The Wideband Output assembly is set for 40 dB attenuation so the 6.5V input results in a 0.032V output into 50Ω. This 0.032V is connected to the RCL line which is routed to the +input of the adc circuit on the DAC assembly. The DAC assembly output is connected to the -input of the adc circuit and adjusted until a null is achieved. This determines the exact value of the Wideband output. This fault occurs if the determined Wideband output is over 6% ±1.0 mV. A failure indicates the Wideband Output (A5) assembly is probably at fault.

3919 Spare

This fault code is not used.

3920 Spare

This fault code is not used.

3921 Spare

This fault code is not used.

3922 A5/A6: Wideband Initialization Fault

This fault occurs if the diagnostics software was unable to properly set the Wideband assembly hardware for diagnostics testing. A failure indicates the Wideband Output (A5) assembly is probably at fault.

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