Fluke 5720A Troubleshooting the Power Amplifier Assembly A16, 32. Waveform at Pin 18 of Hybrid H4

Models: 5720A

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Figure 5-32. Waveform at Pin 18 of Hybrid H4

Troubleshooting 5

Component-level Troubleshooting

1 V

5-22. Troubleshooting the Power Amplifier Assembly (A16) 10 ms Manual background

F5-32.EPS

Figure 5-32. Waveform at Pin 18 of Hybrid H4

13.Connect an oscilloscope to pin 7 of U3B and verify it displays a square wave equal to the positive peaks of Figure 5-32. Next, connect the oscilloscope to pin 1 of U3A and verify it displays a square wave equal to the negative peaks of Figure 5-32. If a failure is detected, check U3 and associated components.

Note

Reinstall the lifted end of R37, solder it to the circuit board, and reinstall the H4 Hybrid cover before continuing.

14.Check the 2.2A current range. Set the Calibrator to 0A in the 2.2A Range by range locking the instrument in the 2.2A range and calling up 0A. Using a DMM, measure the dc voltage across R57 and verify it is 0.028V ±25%. Next, measure the dc voltage across R68 and verify it is 0.028V ±25%. If a failure is detected, check U4, U5, Q11-Q16, and associated components.

5-22. Troubleshooting the Power Amplifier Assembly (A16)

Note

During normal Calibrator operation, internal software monitors the output and makes corrections or trips the instrument to standby. This internal monitoring can cause problems when attempting to troubleshoot the Power Amplifier assembly. Defeat the monitoring by connecting a jumper from TP9 to TP10 on the DAC assembly and another jumper connecting TP1 on the Oscillator Output (A13) assembly to the bottom of R8 (node with R8, C42, C43, and pin 6 of U6) on the Oscillator Control (A12) assembly.

After disabling the internal moitoring loop, remove the rear shield and front air duct from the Power Amplifier assembly. Place the assembly on the extender card and proceed as follows to troubleshoot the Power Amplifier assembly (A16):

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Fluke 5720A service manual Troubleshooting the Power Amplifier Assembly A16, 32. Waveform at Pin 18 of Hybrid H4