Archive for November 24, 2014

Teardown and Repair of an Agilent 33250A Function and Arbitrary Waveform Generator

In this episode Shahriar repairs an Agilent 33250A function and arbitrary waveform generator which does not power on. The unit is equipped with a soft power switch which might be responsible for the fault. After a brief look at the unit’s constructions, the fault is traced to a few possible locations.

The schematic of the soft power circuitry is presented and the internal switching power supply is closely examined. After the fault is located, the repair is presented. The block diagram and operation of a current mode DC-DC switching IC is also presented.

Teardown, Upgrade and Experiments with a Verity Visible Wavelength Monochromator

In this episode, Shahriar upgrades a Verity visible wavelength monochromator model EP200Mmd to be able to perform automatic scans. The instrument is retrofitted with a stepper motor and a microcontroller which performs wavelength scanning between 225nm to 875nm. The signal from the internal photomultiplier is sampled by the microcontroller and wirelessly sent to the computer. Matlab is used to plot the wavelength response.

The principle operation of a monochromator is thoroughly reviewed starting with the grating mirror behavior. The operation of the photomultiplier is also described. Various mechanical and electronic of the upgraded system is also shown. The presented slides can be found here.

Tektronix RSA306 USB Real-Time Spectrum Analyzer Review and Experiments

In this world exclusive episode, Shahriar takes a close look at the all new Tektronix Real-Time USB Spectrum Analyzer. The RSA306 has an RF bandwidth from 9kHz to 6.2GHz with a real-time analysis window of 40MHz. While being entirely powered form a single USB 3.0 interface, it provides a 100% Probably of Intercept for any signal event of at least 100us in duration. The RSA306 is compact, lightweight and shock resistant. At the same time Tektronix has made its Signal-Vu PC software with 17 measurement capabilities free and significantly reduced the price of other Signal-Vu advanced applications!

The SFDR, linearity, noise floor and phase noise of the instrument are all measured and presented. The unit is then used to capture and analyze an intermittent RF interference, analyze and demodulate an RF FM signal using an antenna as well as demodulation a 256-QAM signal with -65Bm of total power.

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