Agilent Technologies 54835A, 45A, 46A Repeat steps 1 through 3 for the remaining input channels

Chapter 5: Troubleshooting

To troubleshoot attenuator failures

Swapping Attenuators

Attenuator swapping is the best method of finding a faulty attenuator. All input channels of the Infiniium oscilloscope use identical attenuator assemblies. The attenuators for channels 1/2 and 3/4 have been manufactured into assemblies to enhance sampling performance. This troubleshooting method provides fast trouble isolation because it is unlikely that multiple channels will experience the same attenuator failure.

Swap suspected and good attenuators, and rerun the tests. The good attenuator can be a separate, known good part, or the attenuator assembly for the other channels of the oscilloscope. If the swap test reveals a faulty attenuator assembly, then install a new attenuator assembly to replace the faulty one, and return the swapped attenuator assembly to its original channels. Following this procedure will maintain the integrity of the attenuator actuation counters.

The attenuator actuation counter is maintained by the oscilloscope software to keep track of the number of times an individual attenuator has switched. Each attenuator is capable of 2 million or more actuations (switches of contacts) before the reliability of the contacts begins to degrade. This provides useful preventative maintenance information for keeping the Infiniium oscilloscope in peak measurement condition. If you replace or permanently swap an attenuator, you may need to reset the attenuator counter. See “To reset the attenuator contact counter” on page 6-30.

Attenuator Connectivity Test

The attenuator assembly scales incoming signals so that the acquisition system can accurately digitize the signal. The Click Test verifies that the relays for switching input resistance and the passive attenuators are working. This connectivity test provides a qualitative assessment of attenuator operation.

1Connect the Aux Out signal from the front panel to the Channel 1 input using a 50 Ω BNC cable.

2Press the Default Setup key, then the Autoscale key.

3The connected channel should display the 715 Hz square wave of the Aux Out signal in both the 50 Ω and 1 MΩ path. If the waveform is not found, or is not stable horizontally and vertically, the attenuator’s internal connectivity is suspect. Swap the attenuator assembly with a new or known good assembly (see “Swapping Attenuators”).

4Repeat steps 1 through 3 for the remaining input channels.

If swapping attenuators into malfunctioning channels does not correct the problem, perform the procedure in “To run the self-calibration” in chapter 4. Then repeat the above procedure for the malfunctioning channels.

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