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John Wiltrout's Blog

140 posts
Thanks to continuing inspirations from so many of my fellow element 14 members I have launched into a project to build a simple DC Electronic Load. I built an Electronic Load once before on a larger scale as that one would handle up to 6 Amps at 35 VDC. In case you are curious here is a link to that blog which is a multi-part series. DC Load Unit "La Carga" Episode I . In the ensuing years since that build I have found my needs for a load were more to the low mA range and the first unit will not ...
I have recently been helping my friend Judy organize and get her Electronics Parts store back on it's feet. This has meant I get to dig through the old stock and reorganize to my heart's content. As I was sorting packages of capacitors yesterday I came across some with and unexplained coil of what looked like solder. The coil was very tightly wound so that it had the appearance of a small spring 1 cm in length. They looked like this:   At first I thought this was a waste as no one would ...
About a year ago I decided that I would try to write an electronics related book. I had written, in the past, simple articles, a couple small books related to dental medical equipment, blog posts on this forum, and a manual for a desoledring station but never anything that would really qualify as a book. Unlike most of my friends on this forum I am not an engineer. I am a self taught technician so my first thought was, what could I possibly write about the would be of any interest to my engineer ...
Today I pulled an old telephone system out of a store that was no longer using it. The one thing that caught my eye was this Harmer Simmons RD 219 Power Supply. It is a beast of a linear power supply with +/- 24 Volts at 4 amps and 5 Volts at 7 Amps.     Weighing in at 11 kilograms it would probably make a pretty good boat anchor. Here are some internal pictures.         Based on the date codes on the chips this is mid 1980s technology and it was probably ...
For a couple weeks I had been on a roll with respect to leaving the basement door exit to the garage open. My shop is in the basement of my home and there are two ways to get into and out of it. The first way is a doorway and stairs from the kitchen area. The second way is a door and stairway up to the garage. It seems that I have gotten into the habit of going out the door leading to the garage with the intention to return immediately. The door itself has a school lock which automatically locks ...
Today I decided that for the fun of it I would smelt the jars of solder tailings that I have accumulated over the last 4 years. I have been very faithful in collecting the scraps and splatters as well as the solder collected from desoldering and salvaging circuit boards. Not only do I want to be environmentally conscious but I also want to avoid the damage that happens to the floors when solder and scraps of metal get embedded into the wheels of the shop chair.   I began the process by mak ...
Yesterday I was working to identify a group of SOT23 transistors that I had just salvaged from a circuit board. After crossing numbers and coming to a good guess of what the transistor was I used the analog meter to check the junctions. With this technique it is easy to confirm whether a transistor is an NPN or a PNP type. The non-slip probe tips make this testing much easier on the lose transistors as I can lock onto one leg and then probe the other two legs without slipping off my contact poin ...
Last night for the fun of it I disassembled a couple of circuit boards like this one:   I am not sure of their function but they seem to be a small receiver that is controlling 2 SPDT Relays whose switch contacts exit on the pins. I have about a dozen of them and the small project box and salvage components looked like a good collection of parts. After they were disassembled I began to ID the parts and among the regular things I found a 3 lead TO92 component marked 7039A-1. A little rese ...
This is a follow up on ntewinkel  blog of a week or so ago:   Nail Polish Short-proofing?   Since I use dollar store nail polish as a circuit sealer and insulator I decided to do some tests to confirm my assumptions that it is a good insulator. Fortunately my new inexpensive Megger arrived a couple days ago so I decided to learn how to use it and test the insulation properties of nail polish at the same time.   The plan was to put some solid wire on a piece of paper separ ...
This is a second chapter from my proto-book. I chose this article as it relates to a question the other day from nickgall2001 about designing circuits. While what I have done in this piece isn't exactly circuit design it is circuit modification and there are some parallels.     From Nothing to Something Adapting a Chinese Kit to a Useful Application               This is a kit from a Chinese source that was advertised as a te ...
  Back in January I began spending time writing short one page to 20 page articles for a book. I hoped to put together at least 50 of these little ideas from an old technician. I modeled them on the short series of blogs I did here on the forum a couple years ago called "Tech Tips". To date I have 54 of these articles. While I have used my home printing  capabilities to put them into book form I find I do not have the drive to rewrite and refine them into anything marketable. With my w ...
jw0752

A Palindrome Resistor

Posted by jw0752 Top Member Apr 22, 2018
     OK this is really not worth writing about but it caught my OCD eye. Perhaps it is the electronics equivalent of a four leaf clover. I will have to buy a lottery ticket tomorrow and check out the hypothesis.     I have done my best to make the colors more readable but they are Brown - Orange - Black - Orange - Brown  (130K).   John ...
I was really pleased today when a project that I have been working on for almost two years had a small success. The Non-Slip meter probe adapters have been a product that was developed and cultivated right here on element 14 with the help of my friends.     There would not have been any chance for even a minor success without you. You took my idea seriously and supported me with suggestions by giving me feedback on the utility of the non-slip tips as well as problems with the design ...
jw0752

Tale of Two Meters

Posted by jw0752 Top Member Apr 12, 2018
Today was a good day as two meters were added to my family of meters. I would not usually write about the addition of a meter or two but the contrast between these two meters is special. Many of you have experienced and appreciate the miraculous development of technology over our relatively short lifetimes. It takes a certain level of understanding and immersion in a technology to really appreciate the change and to truly experience the wonder of the change.   60 years ago I was just begin ...
As if the nice weather wasn't enough of an incentive to move from my home in Wisconsin, where it is currently 10 degrees F and buried in snow, to sunny California, I recently came across this awesome retro electronics component store in Torrance CA.   After I wandered in and started to poke around time stopped. The seeming appearance of chaos to the untrained eye was to me a well packed compilation of 50 years of electronic parts and tools. Another fascination to me was that no one had b ...