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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In my previous post, I did a teardown of an HP 8620C sweep generator along with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin. A few of the plguin boards in the 8620C had leaked capacitors and also there seemed to be some sort of mechanical issue as no power was delivered to the transformer regardless of the power switch positions. So what I planed to do next was to restore the power to the unit and replace those bad capacitors and see if I could bring this sweep generator back to life.
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I just picked up an HP 8620C sweep oscillator with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin on eBay. This time around though, the unit does not work. While it was advertised as a working unit I could not get it powered on and there was no sign of life whatsoever. So before I start troubleshooting and repairing the unit, I thought I would do a quick teardown to see what’s inside and if I could spot anything obvious that was out of the ordinary.
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I recently bought an HP 8671A microwave frequency synthesizer on eBay. This synthesizer can generate signals from 2GHz to 6.2GHz with an unleveled output of more than 8dBm. It is a nice complement to my HP 8642B signal generator and Wavetek 907 signal generator. Using these generators, I can now generate signals of pretty much any frequencies under the 12GHz range. A video of this teardown is linked towards the end of this post.
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My video on the teardown of an HP 493A traveling wave tube amplifier had generated quite a bit of interest. After I revealed that the electron gun portion of the tube was radioactive, a couple of my YouTube channel viewers had wondered if I could take the traveling wave tube further apart. So I did just that.
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In my previous video featured on EEVBlog I did a teardown of an HP 493A microwave amplifier along with the traveling wave tube inside. I actually had done a teardown of an identical unit a while ago but this time I managed to take a peek at the traveling wave tube inside.
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Big thanks to Dave Jones at the EEVBlog for featuring one of my teardown videos. His generosity would certainly help smaller channels like mine attracting more viewers.
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Quite a few people had contacted me on the availability of the firmware for the Amrel PPS-2322 programmable power supply I did a teardown with a few years ago. I finally got a chance to it and backed it up with my TL866A, better late than never. For those who wanted to download a copy of the firmware, you can find the link towards the end of this post.
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As I mentioned in one of my posts a few years back, a color analyzer from the 80’s can be a treasure trove for the hobbyists. And at the very least, it is a cheap way to get yourself a photomultiplier along with the supporting circuitry to do experiments with. For instance, you can utilize the fast response time of a PMT to do accurate speed of light measurement in a lab setting like I showed in this experiment back in 2015.
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I few months back, I wrote about my experience with the six dimmable Philips LED bulbs I purchased a year ago. Those light bulbs all failed within months of each other in just over a year of use. This time around though, it’s the Crees ones that had bit the dust. They lasted a few months longer and were among the twelve I originally purchased. So I decided to open up one to see how the Cree LED bulbs were constructed.
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