Teardown & Repair of an Agilent EPM-441A (E4418A) Power Meter Plus Tutorial on Power Sensors

In this episode Shahriar repairs an Agilent EPM-441A (E4418A) Power Meter. The unit does not boot and displays “Loading firmware…”. After monitoring internal digital signals, the problem is traced to a faulty SRAM IC. After replacement, the unit completes the boot-up process.

Additionally, the principle operation of power sensors is reviewed including both thermocouple based, as well as diode rectifier based. The block diagram of a USB-based power sensor is examined along with a full teardown of a non-functional power sensor. The detector diode circuitry is examine under a microscope. Finally, the repaired unit is verified for calibration.


  1. Alexey says:

    Nice video! Thanks for your posts.
    That diode die just very sexy:). Is it machinned gold or some cheapper metall?

  2. tasweet says:

    thank you Shahriar. i always enjoy your videos. i like that you gleaned enough information from a subtle error to accurately diagnose and fix the power meter.

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