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  1. hevans1944

    Very Nice Portable Oscilloscope/DMM on Ebay 50% OFF

    I have been a "bag dragger" for much of my career, starting with a little green flight-line bag during my Air Force tour of duty, later "graduating" to fiberglass-cased tool sets that survive airport baggage manglers. When I eventually found a nice "office job" with adjacent laboratory, I...
  2. hevans1944

    Very Nice Portable Oscilloscope/DMM on Ebay 50% OFF

    That looks like a bargain if it holds up in the field. I knew a mechanical engineer who had a Fluke meter similar to this one, but it was waaaay out of my price range. He used his for installing and troubleshooting electro-hydraulic servo systems. Quite handy to have something like this in your...
  3. hevans1944

    PC Audio Wiring Assitance Help.

    Oops! My bad. I must have transposed -21 into -12 when I copied it from your image post. So, it looks like you have analog audio on six wires plus a ground (the uninsulated strands of wire in your cable). Now what? Play some music and use an ear-bud (or an o'scope) to find where it comes out...
  4. hevans1944

    PC Audio Wiring Assitance Help.

    I found the wiring diagram below on the Gigabyte website: Unfortunately, the pin-outs don't jibe with your picture. Looks like there is a 3-pin power connector missing.
  5. hevans1944

    Anyone know anything about L46H1 Goodview billboards?

    All I know is what Google reveals: a Chinese Light Box model L46H1 built by Shanghai Goodview Electronic Co.,ltd. Is the image below representative of what you have? Try contacting the vendor directly using information on this web page. I am curious as to why anyone would need a schematic to...
  6. hevans1944

    Looking for a used scope?

    Hey! What's not to like about this? For a measly 175 buckaroos you get (1) a vintage Tektronix 551 dual-beam o'scope WITH (2) a power supply and (3) a connecting "special" cable plus (4) a spiffy roll-about cart with TWO spare plug-in module storage slots and (5) two vertical deflection modules...
  7. hevans1944

    Working With 240v And Arduino

    I can think of "cash crops" a lot more valuable than either peanuts or mushrooms... well, depending on the variety of mushroom. They breed special hogs and/or dogs to locate truffles, so the price per ounce probably compares favorably with other consumable plants.
  8. hevans1944

    Microwave not powering on???

    It should go without saying again, but I will say it again: Be careful working around the high voltage circuits. Make sure you follow the instructions in the manual to discharge the high-voltage capacitor before working with the magnetron. The filament (high voltage) connection between the...
  9. hevans1944

    Microwave not powering on???

    Well, you said the fuse checked good, but does that mean you replaced a previously blown fuse? It is unlikely that the relay coils would be affected by a power-line short-circuit, but any contacts that were in the current path and closed at the time could be damaged, as well as circuit board...
  10. hevans1944

    Microwave not powering on???

    There is, and @Tha fios agaibh described it. You have to apply enough forward voltage to overcome the 0.6 to 0.7 V forward voltage drop of each of the series-connected high-voltage diodes in the diode stack. And then you have to apply the voltage in reverse to make sure the diode stack is...
  11. hevans1944

    Odd Stencil Soldering Problem

    Did you use a hot-air gun to melt the solder paste, or place the board in a re-flow oven? Can you recommend a re-work station? A re-flow oven? I've not tried this assembly procedure yet, but it looks like you may have used way too much solder paste on the board, and maybe not have had a firm...
  12. hevans1944

    help designing triggering device for underwater camera

    There is already a TEST push-button switch that is part of the camera circuitry. This switch shorts pins 3 and 4 together when it is pressed. Try pressing this switch to see if there is anything wrong with the circuit before adding a few hundred feet of cable.
  13. hevans1944

    Noise Activated Switch, with a Difference.

    I really like the piezo chirper idea. Better even than Bluetooth, and a LOT cheaper. Closed doors might be a problem, as you mentioned, so the user might have to run some bell wire (tape it to the walls) from the room with the light to the room with the microphone and operate the lamp from a...
  14. hevans1944

    2 transistor oscillator

    What part of the text are you reading that "says I should hear a changing in the oscillation"? The frequency of the oscillator is varied by changing the value of R1 or C1. Smaller values (within certain limits) will result in higher frequency of oscillation and larger values (again, within...
  15. hevans1944

    Microwave not powering on???

    Post a wiring diagram.
  16. hevans1944

    Noise Activated Switch, with a Difference.

    Another, probably more expensive, solution is to fit three Arduino Uno modules with XBee Bluetooth shields. Interface each Arduino to either the telephone or the doorbell circuits, with the third operating the signaling device through the Bluetooth communications interface. You can add as many...
  17. hevans1944

    Microwave not powering on???

    Gee, what a nice feature, a drawer that slides out! And costs only $900 more than a 1200 watt microwave with a door that opens sideways.:rolleyes: Country living at its finest!
  18. hevans1944

    Working With 240v And Arduino

    Could you upload an image showing the entire "~20 watt heat cord"? The "cord" you cut looks like coaxially shielded wire of some sort, perhaps with "resistance wire" as the center conductor. It is probably shorted internally between the center conductor and the shield on the end farthest from...
  19. hevans1944

    Need Electronics projects for 8 year old

    An Arduino is a small Atmel microprocessor mounted on a circuit board with additional components to allow interface to the real world. It requires a personal computer (PC), connected to the Arduino via a USB cable, to program it in a "C"-like language. After the program is downloaded to the...
  20. hevans1944

    Need Electronics projects for 8 year old

    I think the solderless breadboard approach to learning is a good way to start. These are simple devices that come in various sizes and support a wide variety of components. I have a dozen or so in my stockpile, some with circuits still attached that are functional after many years. While...
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