Kerry D. Wong

Typically, a lab power supply can only operate within a single quadrant. Take a positive voltage power supply for example, it can only output or source current. If any attempt is made trying to sink current into the power supply by connecting a voltage source with a higher voltage than the output voltage of the power supply, the power supply would lose regulation since it cannot sink any current and thus is unable to bring down and regulate the voltage at its output terminals.
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Have you ever wondered what is inside of a 15 year old commercial color projector? Well we will find out in this post today. As usual, a video of this teardown is included towards the end of the post.
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I recently bought a few Peregrine Semiconductor‘s PE42420 RF Switch evaluation boards on eBay. The PE42420 is an absorptive SPDT RF switch that operates between 100 MHz and 6 GHz. Besides the obvious use as a single pole double throw RF switch, we will take a look at using it as an RF modulator due to its fast switching time (~300 ns) in this post. A video of the experiments discussed in this post can be found towards the end.
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I did a teardown a while ago on a cheap eBay electromagnetic radiation detector, and if you recall the performance of that meter was mediocre at the best. This time around though, I’ve got a MEDA PLM-100 AC magnetometer. Since MEDA (Macintyre Electronic Design Associates) specializes in fluxgate and search coil magnetometers, this PLM-100 magnetometer is a piece of professional test equipment. In this blog post, you will see some teardown pictures and for those who want to see some real world actions you can take a look at the video included towards the end.
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IRIG time code generators (not to be confused with the ones used in video and film industry) are often used for clock synchronization among various connected equipment and is commonly used in power generation and distribution industry as well as in the military. In this blog post we will take a look inside a Datum 9300 time code generator from the late 80’s. A video detailing the teardown is linked towards the end of the post.
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I recently found a Hittite (acquired by Analog Devices in 2014) HMC624LP4E evaluation board gathering dust in my miscellaneous PCB bin and thought it might be a great little project to add a microcontroller interface to it so I can use it as a convenient digital attenuator in my lab. The HMC624LP4E had been replaced by Analog Devices’ HMC624A-EP but these two chips are mostly identical so everything described in this post can be applied to the newer HMC624A as well.
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I bought a USB wall outlet adapter recently so that I can free up my wall outlets while charging my phones and tablets. Of course, before putting it into use, I wanted to open it up to take a peak inside to see if it was properly engineered and at least to make sure that it would not be a safety hazard at the least. After all, this USB adapter is meant to be plugged in all the time.
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Recently I got hold of a dead APC SurgeArrest power strip that was about to be thrown out in my office. The power strip simply doesn’t provide power to any of its outlets regardless of the power switch position. Since there was no external fuse that I could find, I decided to take it apart and find out why and how it had failed.
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In my last post, I did a teardown of the Keithley 775A programmable counter/timer. And while feeding a 10 MHz signal from my Rubidium frequency standard, I noticed that the measured frequency was significantly lower (9.9981 MHz) than the nominal 10 MHz reading and could not be compensated by adjusting the TCXO fine adjustment screw alone. My suspicion quickly turned to the temperature controlled crystal oscillator (TCXO).
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I just picked up a Keithley 775A programmable frequency counter from eBay. Specification-wise, this counter is very similar to the Racal Dana 1992 frequency counter I repaired last year. The Keithley 775A I got came with an additional channel (option 7751) and is capable of measuring frequencies up to 1.3 GHz.
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There are a lot of cheap electromagnetic radiation testers out there which boast some quite impressive claims. So I decided to pick up a popular one (GM3120) from eBay to see how well it works. And perhaps more importantly, I wanted to take a look inside to see how the E field and H field sensing is done.
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While I was making a video on how to use HP 8671A as the frequency reference for an improved version of my simple DIY tracking generator for my HP 8566B spectrum analyzer, my spectrum analyzer suddenly decided to call it quits and displayed the dreaded “YTO Unlock” message. Although it wasn’t the first time it had done so — other times the “YTO Unlock” message only appeared once in a blue moon and rarely affected any measurements — this time however the problem seemed to be permanent and the error message wouldn’t go away.
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I recently received an M5Stack ESP32 development kit from Banggood. Although I have not used any ESP32 based development boards before, I have heard many good things about the ESP32 platform, especially for its rich feature set and versatile connectivity. After all, it was designed to have IoT applications in mind. So I was pretty excited to take it for a spin.
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Although LED light bulbs have been around for a while, I have not been able to totally replace all my lights in the house to LED ones until quite recently. The main reason is that some of my existing light fixtures only take G16.5 style bulbs with E12 screws and higher wattage LED bulbs of this kind only became available until quite recently.
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Differential amplifiers come in handy in applications where common-mode noise and interference are present in the system. This is largely attributed to the very high common-mode rejection ratio (CMRR) these amplifiers provide. And because of the high CMMR they are well suited in high-side current measurement applications and in situations where voltages must be measured deferentially. So over the past couple of weeks, I made a differential amplifier PCB based on TI’s INA117 and it will serve as building blocks for some of my future projects.
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