Kerry D. Wong

The latest addition to my lab equipment is a Keithley 230 programmable voltage source which can output up to ±100V. Unlike many of the power supplies and voltage sources I have, the Keithley 230 is capable of operating in all four quadrants, meaning it can both source and sink current in either of the output polarities. Although the current capability is limited to ±100mA.

I recently picked up a downconverter box on eBay. My original plan was to use the enclosure for another project as it has a very nice aluminum enclosure. Naturally of course, I wanted to take a look at what kind of downconverter this one is and how it works first.

Electrophoresis power supplies are commonly found in biology and other life sciences laboratories. These power supplies are usually capable of supplying high voltages and high currents required for gel electrophoresis–a method used for separating DNA, RNA and other protein fragments based on their size and charge. There are many used electrophoresis power supplies out there in the second hand market and can be bought quite cheaply. I am curious whether these electrophoresis power supplies are suitable for electronics lab use as a lab grade high voltage power supply can be quite expensive. So I recently picked up one from eBay to take a look.

In my previous blog posting, I did a teardown of a LogiMetrics A300/S 2 to 4 GHz Traveling Wave Tube Amplifier (TWTA). After doing the teardown, my focus immediately turned to troubleshooting the unit and hopefully restoring the unit back into working order again.

I just picked up a LogiMetrics A300/S 2 GHz to 4 GHz (S band) traveling wave tube amplifier (TWTA) on eBay. I had done an extreme teardown of an HP 493A TWTA a while ago and it was quite fascinating to see what’s inside of a TWT. This LogiMetrics A300/S was made from the late 70’s and unlike the HP 493A it was made entirely using solid state devices (e.g. transistors and ICs), the TWT itself of course remains a vacuum tube.

Monochromator is one of those things that has always fascinated me. Over the years, I have done quite a few experiments (I, II, III) with an EP200Mmd monochromator and it was a lot of fun. Because monochromators are such highly specialized equipment, decent ones are hard to come by at reasonable prices second hand. So my strategy has been to scour eBay once a while and pick up bit and pieces whenever I can.

I was doing some experiments which involves switching high voltages (>3 kV) under high current (>30 Amps) load. Although solid state devices such as SCRs (Silicon Controlled Rectifier, or Thyristor) or IGBTs are the ideal candidates for this kind of operations, the prices for these devices are through the roof (1, 2) when the breakdown voltage exceeds the 3kV threshold. I did have a couple of QIS6502002 6500V 25A IGBTs I bought on eBay many years ago but as it turned out they were quite fragile, a few minor overloads during my experiments was enough to destroy them unfortunately.

Gyroscopes nowadays are based on micro-electro-mechanical systems (MEMS) technology. They are low cost and extremely miniaturized. A device combing both a three-axis gyroscope and a three-axis accelerometers (sometimes these devices are referred to as 6DOF devices) such as the MPU-6500 for example can be had in a QFN package as small as 3 mm x 3 mm and under 1 mm in height. Before these MEMS devices gained mainstream popularity however, larger piezoelectric vibrating gyroscopes were used in many consumer electronics devices.

In my previous post, I designed and 3D printed a high voltage connector for my Bertan 225-20R high voltage power supply. The silicone high voltage wire I ordered had finally arrived so I made a couple of cables using the connectors I printed. A few of my viewers had questioned the suitability of using PLA as printing material in high voltage applications so I decided to measure the dielectric breakdown voltage of PLA and gather some real-world data. Continue reading ‘PLA Dielectric Strength Measurement’ »

In one of my previous posts, I did a teardown of a Bertan 225-20R high voltage power supply, which is capable of outputting 1mA with an adjustable voltage range up to 20 kV. The power supply came with a special high-voltage connector however (similar to the CMC series connectors from Connectronics Corp), but I wasn’t able to get a mating connection cable. At least not at a reasonable price. Continue reading ‘3D Print an HV Connector’ »

In my previous post, I did a teardown of my Array 3711A DC electronic load. And as I promised, this time I did some testing with it and also discussed some tips and pitfalls. Continue reading ‘Array 3711A Electronic Load Testing – Tips and Pitfalls’ »

I have made many electronic loads in the past. For instance this simple harddrive cooler housed small dummy load, this more sophisticated constant current/constant programmable load and this heavy-duty electronic load that is capable of sinking over 1kW under peak load. In this blog post though, I am going to take a look inside an Array 3711A DC electronic load I recently purchased on eBay. You can find a video of this teardown towards the end of the post. Continue reading ‘Teardown of an Array 3711A 300W DC Electronic Load’ »

A couple of weeks ago, I got myself an Agilent U1731B LCR meter on eBay. These handheld LCR meters are quite expensive when new, but can be found on eBay for a fraction of the original price. Dave Jones at the EEVBlog did a teardown video on a better spec’d U1733C (and U1733B) meter a few years ago, I suspect that circuit-wise the U1731B would be quite similar to what’s inside of a U1733B. Continue reading ‘Agilent U1731B LCR Meter Teardown’ »

I recently bought a Noritake-itron VFD module off eBay. Noritake-itron specializes in making vacuum fluorescent displays for many OEMs. As such, there are many surplus modules being sold in secondary markets. The module I got has the model number CU20026SCPB-T26A, but unfortunately there’s not much information available on the internet for this specific model. Continue reading ‘Interfacing a Noritake VFD Module with Arduino’ »

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. Continue reading ‘Inside an Agilent 66312A Two-Quadrant Power Supply’ »