Kerry D. Wong

I got a Wavetek 395 arbitrary waveform generator (AWG) last year. Unlike my other equipment (such as HP 8566B, HP 5350B, HP 8642B and Racal Dana 1992) which all came with high stability ovenized crystal oscillators, the Wavetek 395 only comes with a 100ppm crystal. While the stock timebase is perfectly fine for all but the most serious measurements, I decided to upgrade it to an oven controlled crystal oscillator (OCXO) as I happen to have a Vectron CO-717B58N lying around.
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I picked up an HP 7044A X-Y recorder on eBay recently. This one was made in the early 1980’s and by today’s technology standard it is rather ancient. And because of this, it is very easy to interface with as the input is completely analog. My plan was to do some experiments down the road using the X-Y movements capability of this HP recorder.
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Till recently, I have been using custom circuitry whenever I needed to backup some firmware. But the process was rather tedious as for each kind of EPROM or EEPROM I needed to study the protocol and timing requirements and then come up with the required circuitry on a breadboard. And wiring can easily become an issue with a high pin-count chip. So I finally got myself a proper EPROM programmer (it’s a TL866A) along with a $15 generic UV EPROM eraser so I could program EPROM/EEPROM’s quickly. While it was fun to build a programmer circuit each time, I think the effort can be put into something more useful.
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I got this broken Beats Solo2 BT wireless headphone from one of my colleagues. In fact, it was broken once before around two years ago and I fixed it for him back then. The issue was because of a broken signal wire due to repeated flexing of the collapsible headphone band. This time around though, I am not going to fix it although I suspect that the cause remains the same. In fact, quite a few of my friends with the same Beats headphones had experienced similar problems. So I wanted to take it apart and take a closer look inside. A video of this teardown can be found towards the end of this post.
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In my previous blog posts, I did a teardown of the Symmetricom/Datum 8040 Rubidium frequency standard and modified the 1PPS output by expanding the pulse width from just around 10µs to roughly 50% duty cycle. There were some questions regarding the clock jitter introduced by the 555 monostable circuit. So let’s take a more detailed look in this post.
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Last time, I did a teardown of the Datum 8040 Rudidium standard. As I discussed, the 8040 has a 1PPS output but the pulse width is very short, at around 20µs. In this blog post, let us take a look at how to extend this 20µs pulse to make the 1PPS output symmetrical. As usual, a video is included towards the end.
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I finally got my hands on a Rubidium frequency standard. I have been wanting to get one of these for my lab for quite some time now but have not encountered a good one at a reasonable price. Most rubidium oscillator modules on the second hand market these days come from decommissioned equipment used in cell towers. A good used lab grade rubidium standard is even more expensive.
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I picked up a non-working Racal-Dana 1992 Frequency Counter on eBay a few weeks ago. The symptom is that only channel C seems to work correctly and neither channel A or channel B produces any measurements. Since the majority of circuitry is shared among all three channels, it is most likely that the fault is localized within channel A and/or channel B. In this blog post I included many teardown pictures taken during the repair and a video detailing the process is included towards the end.
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I got myself an HP 5350B microwave counter a couple of years ago and did a teardown of it. The backlight on the LCD is pretty weak and does not provide much contrast however. So I thought I would upgrade the backlight with a few white LEDs and see if I can make the display easier to read.
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I bought a couple of IXYS linear MOSFETs (IXTK90N25L2) a while ago to test their capabilities when used as electronic load, and the result was quite impressive. So I decided to build another electronic load using both MOSFETs. As you can see in the video towards the end, this electronic load can sink more than 100 Amps of current while dissipating more than 400W continuously and can withstand more than 1kW of power dissipation in pulsed operation mode.
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In this blog post, I will show you a simple hardware hack to make your mouse capable of rapid firing (or automatic continuous clicking). Of course you can always resort to software mods to achieve the same goal, but admittedly doing so in hardware is nevertheless more fun and as a bonus you also get an extra button. A video demonstrating this hack can be found towards the end.
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I just picked up a charger along with a couple of NP-FW50 spare batteries for my new Sony Alpha A6000 mirrorless digital camera. The Sony branded charger is ridiculously expensive, so I opted for an aftermarket Vivitar branded one (VIV-QCB-104), which retails for under $10. The charger is rated at 8.4V with maximum charging current of 600mA. Spec-wise, it looks fine for the NP-FW50 1Ah 7.4V battery pack.
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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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