TSP #222 – Teardown & Repair of a Fluke 5450A Precision Resistance Calibrator (1-Ohm – 100-MOhm)

In this episode Shahriar takes a look at a non-functional Fluke 5450A resistance calibrator box. The unit is equipped with a wide range of resistors ranging from 1-Ohm to 100-MOhm some of which are 0.005% tolerance. The instrument powers on and shows a single LED on the front panel without any other activity.
Upon further inspection it becomes clear that there are no other activities from the main CPU despite the clock signal being present. A replacement CPU returns the unit to normal front-panel operation. The analog board also has two blown fuses which may be the result of a in-rush event. After fuse replacement the analog relay arrays also function. The unit is measured against a Keysight 3458A 8.5-digit multimeter and shows remarkable accuracy despite its age.


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