This circuit could be used for blind to sense light. It’s a similar circuit to the police siren. The two transistors have a current gain of 200 X 200 or 40,000 so even a very tiny Q1 base current – microamps – causes a very large Q2 collector current. So a very small amount of
(Read More…)
I use this for holding solder while I hold the PCB and iron with my hands. I use my teeth to hold this pen.
Caps Wiki – a place for you to share your repair notes. I like the idea. I’m wondering if I have the patience to spend the extra time. https://hackaday.com/2022/02/24/caps-wiki-place-for-you-to-share-your-repair-notes/
This is a 5 transistor ESR meter for testing capacitors. https://eevblog.com/forum/projects/5-transistor-esr-meter-design/
Last week I saw an old Heathkit IP-18 power supply on eBay for $50 OBO, free shipping. I don’t really need another PS, but I’m a Heathkit builder and a big fan. So I offered $30, thinking the seller would not take it. But a few hours later the message came that the seller had
(Read More…)
Its not hard to make a signal tracer from an old AM radio. You need 60 mm of red and black flexible twisted pair, a 0.22 uF, 100V capacitor, a small black alligator clip, a 50 mm length of shrink tubing that will fit over the following probe, and a thin 100 mm long piece
(Read More…)
I got this frequency counter and crystal tester mainly for the frequency counter. Today I decided to test a few crystals, and was successful with ones above 10 MHz but not at 4 MHz. The two capacitors labeled C2 and C3 are the feedback to the crystal, and they were originally 22 pF. So I
(Read More…)
Here is a writeup from another radio enthusiast about his newly purchased Mega 328 uC based component tester. They come in handy for testing electrolytic capacitors especially for ESR – equivalent series resistance. The tester will also test silicon and germanium transistors, handy for making a judgment on how leaky it is. I have a
(Read More…)
This is from Electronics Illustrated Projects 1968. It shows crystal sockets, but instead a RF coil may be used and its value will be about 220 microhenrys. And C1 and C2 will have to be changed to bring the frequency down to the AM band. The germanium transistors are no longer available so silicon transistors
(Read More…)
From fb group Decades ago I bought a 100W, 28V big old soldering iron for a dollar at a garage sale. I have it connected to a big old unregulated power supply. It works good for the very seldom times I need that much heat. I could do stained glass windows with that beast!
