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  1. John Canon

    Are Deoxit contact cleaners worth the money?

    Is that in 2017 currency or 2022 ?
  2. John Canon

    Need help designing a solar powered rechargeable device

    Is this to light up a garden pathway? They already have those units, some of them look like Gnomes or Mushrooms.
  3. John Canon

    Mentor for Electronics

    You can start right away. First post a good drawing of the circuit. Then tell us what parts you have found, how large it will be, and what you will use it for. You may as well start with your current project.
  4. John Canon

    SUN GDM 20E20 CRT Monitor Screen Tired my Eyes Help

    The first thing that comes to mind is the refresh rate ... if may have changed accidentally. If it is too slow it can cause symptoms. Then check other things: are you sitting closer, is there glare or reflections on the face of the screen? Last year I gave up my Viewsonic Professional CRT...
  5. John Canon

    UPS with too much boost

    Over the past week I run the UPS on my test bench, specifically monitoring the input and output voltages. The unit seems normal, and the line voltage has stayed around 116 to 118 vAC. I have not seen 109 vAC since that one day. When it happened the voltage would go down to 109 volts for about 20...
  6. John Canon

    Why do some devices turn on with the mains before the "On" button is pressed?

    The sudden application of power will cause a small surge to the various capacitors in the device. The inrush will then cause solid state devices to receive false triggers unless there is good circuit design to prevent these false triggers The 2 cheap Asian consumer products you own obviously do...
  7. John Canon

    Have 3,3V need 15V

    The 0.7 voltage drop is an inherent characteristic of the P-N junction. It is always 0.7 volts regardless of the current flow. Imagine a one-way water valve with a spring loaded flapper. The spring pressure in the valve is similar to the voltage drop in all diodes. Now I am waiting for someone...
  8. John Canon

    UPS with too much boost

    I have a MinuteMan standby UPS 1500W unit for my entertainment center. It has a single stage buck/boost. Recently, several times per day, it would click and the output voltage would read 134 volts AC. Most SMPS would accept that, but I noticed my box fan revving up speed. I think the unit is...
  9. John Canon

    Replacing tiny IR LED

    The little circuit board is in the middle, surrounded by 3 AA cells. There is a lot of flexing whenever I swap out the rechangeable NiMh batteries. The unit is back in service now, and I know where to look if one of them fails again. Thanks for the good tips.
  10. John Canon

    Replacing tiny IR LED

    The pins are far away from anything, but you are probably right about a micro-crack. I will use my magnifier if it acts up again. One of my current projects is a high power IR illuminator for use with security cameras. Not tiny. It uses "dark IR" of 940 nanometer wavelength. The instructions...
  11. John Canon

    Replacing tiny IR LED

    I knew you were going to ask me that. I opened up a good unit and, lo and behold, it was 3.7 volts. So I went back to the non-working one ... 3.7 volts, and operatonal. So I put it together with the 3 pin rivets and ... not working. I started to remove the 3 pins while keeping the batteries in...
  12. John Canon

    Replacing tiny IR LED

    I have several of the Sylvania Golden Dragon motion sensing battery op lights for under cabinet use. One has failed and I suspect the IR diode. When I aim my digital camera at it, it is dark. But on other units I can see the dim purple of the working diode. On the circuit board I can measure...
  13. John Canon

    Practical, simple circuit and method in make our own oscillating volt meter

    Are you trying to choose between several possible circuits? Do you have a simple block diagram of your testing procedure? What have you figured out so far? A more specific question about your setup could start a discussion.
  14. John Canon

    Detection of electronic device

    Sorry to hear about your 2 dogs. Probably not caused by any device, but you could build the detector I had described just to be sure. And save the shielding for yourself.
  15. John Canon

    Detection of electronic device

    I once wired a small ultrasonic speaker as a microphone, and fed the signal into an oscilloscope. I tested it on one of those rodent repellers and, yes, it showed the signal. I could also calculate the frequency, about 40 kHz.
  16. John Canon

    Power Supply Clarification

    Good. The diode circuit above will allow power draw from one or both. The 0.7 volt drop is nominal and should cause no problem unless your device is medical equipment or satellite transmitter. hehe. Choose rectifier diodes with minimum 5 Amp and 50 volt ratings
  17. John Canon

    Power Supply Clarification

    This circuit allows Supply A, supply B, or both to provide power to the output, automatically isolating the 2 supplies from affecting each other. If you want to control which supply is being used while both are connected, then a SPDT switch is all you need, and no diodes. You haven't told us the...
  18. John Canon

    Power Supply Clarification

    How to do it ...
  19. John Canon

    Carbon ribbon cable repair

    If I had to fix it here is what I would do. Find a small piece of glass or plexi about 2 cm by 8 cm. Epoxy the two cables so the conductors line up tip to tip, facing each other. Almost like you were splicing an audio tape. Next take some fine sandpaper or a curved exacto blade and scrape the...
  20. John Canon

    Carbon ribbon cable repair

    How good are you with an Exacto knife? Oops, forget I said that!
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