Kerry D. Wong

I just picked up another high voltage power supply, this time it is a working Bertan/Spellman 225-20R 20kV one. Unlike the Bertan 205A-05R that I did a teardown with last time which was entirely analog, this one can be controlled digitally either via the front panel or via GPIB from the back. In this blog post, let me share some of the teardown pictures with you. If you are interesting in seeing some cool experiments with this high voltage power supply, you can scroll down and watch my video towards the end.
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I got a non-working Bertan 205A-05R 5kV high voltage power supply and did an attempted repair video a while ago (see video towards the end). But I forgot to post my teardown pictures somehow. So here we go, better late than never.
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I have always wondered how the clean/dirty indicator on my Hoover vacuum cleaner works. So when it was time to replace it with a new one, I opened up the old vacuum and took out the “dirt finder” circuit board. As you will see in the video below, it is actually quite clever!
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In my previous post, I discussed why it is beneficial to use linear MOSFETs in electronic load and performed a couple of experiments using a single IXYS’ IXTK90N25L2 linear MOSFET. The electronic load was able to dissipate around 150W before the case temperature of the MOSFET reached 90°C.
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Power MOSFETs are widely used in switch mode applications such as pulse width modulated electrical motor controllers and switching mode power supplies. While they are also routinely used in linear mode applications such as power amplifiers and linear power supplies, standard MOSFETs are prone to secondary breakdowns due to hot-spotting or current focusing when operated in linear mode.
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A while back, I added a fan controller to my Topward 6603A power supply. Later on, when I bought a used programmable power supply (PPS-2322) I had to do the same thing. Both of those builds were done on protoboards but I had a feeling that many of my other projects could use a similarly designed fan controller as well. So I thought why not just have the PCB professionally made?
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Static fieldmeters (or electrostatic fieldmeters) are typically used for non-contact measurements of the electrostatic field strength (usually in kV) of charged objects. These are highly specialized test instruments and most hobbyists probably seldomly have the opportunity of coming across one. So in this post and a companion video towards the end, we will take a look at how it works and what’s inside.
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I did a teardown of a SMART UF-55 DLP Projector a while ago, and later I showed how to hack the ballast board so that the discharge lamp could be powered without the rest of the projector circuitry.
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Not all cables have proper strain relief built to the connector ends. This is particularity true for some of the iPhone 6 USB to Lightning™ cables. Take this Anker branded iPhone cable for example, after several months’ normal use the cable towards the USB end started to show signs of excessive strain (see image below). The internal wiring would soon be damaged if the strain on this area continues.
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I recently was given a broken Epson PowerLite 84 projector. The projector would not turn on when plugged in and there was no sign of life. So I decided to take a look at what was wrong with it. The potential reward is high since I do not have a projector yet and I could definitely use one for my home theater setup. A video of this teardown and repair is linked towards the end.
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I picked up a Wavetek 395 arbitrary waveform generator on eBay a few weeks ago. Wavetek 395 is a single channel, 12-bit resolution DDS AWG with a maximum clock frequency of 100 MHz. While the operation manual is readily available, I could not find the service manual anywhere. So I was curious to see the construction inside. In this post, I will show you some of the teardown pictures. If you want to see a video of the teardown along with some analysis, you scroll towards the end of this post.
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After taking the SMART UF-55 projector apart, I decided to take a look at the salvaged circuit boards to see whether I could re-use them to power the projector discharge lamp. Most of the modern projectors utilizes some kind of “smart” ballast circuits so that the main board could communicate with the ballast to determine the correct drive level given the required luminous level and monitor the operating temperature.
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My workplace was throwing away an old SMART UF-55 DLP projector. The projector had many stuck mirrors and the lamp had already surpassed the rated useful life span. I had always wanted to take a look at a DMD chip so I decided to take it home and do a detailed teardown. You can find my video of this teardown towards the end of the post.
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I bought a non-working Lambda LQ-521 linear power supply on eBay a couple of weeks ago. Usually I avoid knowingly buying something that is broken unless I am certain that I could obtain parts for it at a reasonable price. But buying broken linear power supplies is another story as most of the problem can be fixed with readily available components.
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I did a teardown of an RSA SecurID many years ago (you can see that post here). In that teardown, it was an older generation (SD600) of the RSA SecurID. In this post, let’s take a look at what’s inside the newer SID700 series RSA SecurID token. A short video of the teardown is included towards the end.
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