I was asking about very old capacitors and their shelf life on FB vintage test equipment group. The guys tell how good the old capacitor testers are because they have the “magic eye” to check for leakage. I was thinking that it would be easy to test any capacitor for leakage. All that’s needed is
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I pulled a pill bottle out of my junk box, it had a single layer of solid enameled wire wound on it, and it measured 85 microhenrys. So I added the transistor, resistors and the capacitors to get it to oscillate at the low end of the AM BCB, around 540 kHz. The schem is
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From a comment in FB group I buy most stuff from Mouser because I found their prices are lower than Digikey. I’ve had bad experiences with mouser, mostly shortages on quantity, but I had some disc caps thar were below tolerance. Mouser has some cool ways to narrow down the selection to a manageable size.
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After I unsoldered the parts from my failed ‘noisy regenerative receiver’ circuit, I decided to build a more conventional regenerative receiver, one that uses a single transistor for the regenerative stage. I chose the circuit from a website that I had found, and saved the schematic. But I forgot to document the URL of the
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I got a few of these just to satisfy my curiosity, and to waste ten bucks each and waste time sorting the transistors into piles of the same number. My general observations Most of the datasheets for these transistors can be found online. Most of the transistors are PNP. I got several dozen, maybe a
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I watched this YouTube video where the author shows his FM transmitter using a big 60 volt power MOSFET. He also shows a very readable photo of the schematic. The video was made several years ago in 2012. He is powering this transmitter by connecting it to eleven 9 volt batteries in series, totalling 99
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I went online a few days ago and looked for some odd RF transistors, but instead I was shocked. Almost all of the parts I’ve been using are through hole parts, like transistors in a TO-92 package with wire leads. I looked at a few distributors such as Mouser, Avnet, Arrow, Digikey, Newark. I found
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I put this AA cell, which measured 1.3 volts – ‘dead’ – on one of my germanium Joule Thiefs more than a week ago. It was glowing very brightly for a few days. For the last few days, it has been weakly glowing, and the Kirkland AA cell is still hanging in there, even though
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I have always thought that using ferrite toroid cores for radio projects at HFs and above was not necessary, because all of the RF circuit parts lists call for low permeability powdered iron cores. I’ve never given it much thought; about the only thing that crossed my mind was that the powdered iron cores may
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It has been a long time since I designed Blue Blinky; I just wanted to update it. I have used a 1 uF electrolytic capacitor for the timing capacitor, and it works just fine with the two 680k resistors to give about 1 per second flash rate. I got a bag of hundreds of multilayer
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