In this episode Shahriar takes a look at a new dumpster find! A Photo Research PR-670 SpectraScan has some unique capabilities for measuring light spectrum. In particular, it has an adjustable field of view, as narrow as 0.125 degrees, which allows the spectrometer to ignore the majority of light sources in a scene and only focus on a small visible area. This means it is possible to measure multiple points of a screen or sources of light from far away.

The teardown & theory of operation of the instrument is presented including the spectrometer core which uses a diffraction mirror and linear CCD detector. A few experiments are also conducted which showcase the FOV measurement capability using an array of RGB LEDs. Lastly, the measured spectrum of a mercury discharge lamp is also shown.

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In this episode Shahriar explores the capability of some frequency counters to measure DC voltage. While this may seem non-intuitive initially, the video shows how the architecture of the HP 5245L Nixie tube frequency counter can be used to realize an integrating ADC. A particular plug-in module, the 5265A, leverages the Start/Stop counter control to implement an ADC and display the equivalent DC voltage at the plug-in input. The theory of operation as well as the teardown of the plug-in in shown.

The plug-in module unit is zeroed & calibrated initially and then using a Fluke 5720A the performance of the entire system is evaluated. Despite being in storage for decades, the unit is incredibly accurate and precise.

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In this episode Shahriar attempts the repair of a Keithley 2510 TEC Source-Meter. This instrument is capable of delivering up to 60W of power to any TEC in both polarities. Furthermore, the instrument integrates a flexible temperature read-out capability with 4-wire interface. Lastly, combining both capabilities, alongside a fully customizable PID controller, a precise temperature controller can be realized.

This particular unit returns erroneous readouts in all modes: voltage, current, resistance & temperature. The unit is also generating "squeaky" noises which is indicative of a failing DC-DC converter. The block diagram of the unit is examined and the fault is ultimately traced to a damaged opto-isolator in the isolated switching power supply. Several other components are also faulty which are located via thermal camera. The output Class-D / buck converter circuit & block diagram are also examined in details.

Unfortunately, the custom IC at the heart of the multi-slope ADC is also damaged. The IC is de-capped, examined under a microscope, and compared with its predecessor CPLD counterpart. This Keithley component is sourced from an older high-speed power supply. The correct readout is then verified. Several experiments are demonstrated using the PID controller and a custom TEC setup.

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