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  1. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    SPI is serial (that's what the "s" stands for, after all), but it is synchronous - there is an explicit clock signal (SCK). Generally, "serial data" (like the data used with a serial port, with start and stop bits) is asynchronous; a single data signal, with character framing (the start and stop...
  2. KrisBlueNZ

    24VAC power supply question about VA spec

    Cool! That's brilliant. Good work!
  3. KrisBlueNZ

    What Is The Ohm Of This Resistor

    I don't think you can tell anything from the colour bands of a resistor in that condition. Have you tried to find service information for the unit? Can you post a photo of the board? If we can figure out what part of the circuit it is in, we might be able to suggest an appropriate value to try.
  4. KrisBlueNZ

    Another treadmill problem

    Good idea Steve. Yes, he needs to check the MOSFET and the diode before applying power; I didn't say this explicitly but I said that if they were faulty, they could have caused the resistor to fail. I assumed he would grok the implications of that!
  5. KrisBlueNZ

    24VAC power supply question about VA spec

    Sorry, no, the two pads that need to be connected together are at the two ends of the diagonal green line in my picture. One of them is one side of the resistor you need to remove, and the other is on a different component.
  6. KrisBlueNZ

    Another treadmill problem

    OK. Here's what I've figured out so far. Don't worry about any words you don't understand; this is mainly for my own reference! Mains is bridge rectified and smoothed by two 560 µF electrolytics, to provide DC to the treadmill motor (90V DC motor). The motor is controlled using PWM, switched...
  7. KrisBlueNZ

    24VAC power supply question about VA spec

    Yep. Remove the resistor marked 472 and connect the two pads together as shown.
  8. KrisBlueNZ

    HP 1741A Oscilloscope

    I saw that article on the discrete CA3094A as well. I agree with the critics that it's not a good idea. You mentioned CP3094A twice in your previous post. It's CA, not CP. Just making sure that you're using the right search term! It might be possible to use a CA3080 with some external...
  9. KrisBlueNZ

    24VAC power supply question about VA spec

    Yes I think I'll need a better picture than the one on the auction page. Can you put a bright light on it and take a close-up. I only need the section from the edge of the relay up to the far end of the 8-pin IC.
  10. KrisBlueNZ

    Another treadmill problem

    OK, that's a good start. It looks like the AC mains supply is rectified by the MP3510S bridge rectifier on the heatsink, and smoothed by the two large electrolytics, then fed to the motor with two or three components in series. We need to find out more about these components. There seem to be...
  11. KrisBlueNZ

    24VAC power supply question about VA spec

    Oh dear. Yes, it looks like it's a delayed closure, not a timed pulse closure. Sorry! I can't find anything suitable on eBay! Luckily, you can modify the board to do what you want. 1. Remove the circled device (a 1 kilohm resistor, marked "102") on your board. You can cut it in half with a...
  12. KrisBlueNZ

    HP 1741A Oscilloscope

    It's A15U1.
  13. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    Are you talking about asynchronous serial communication with slave units or SPI communication with LED drivers? SPI doesn't use start and stop bits. You have a clock signal, which is generated by the master (your MCU), and a data signal from the master to the slave (sometimes called MOSI...
  14. KrisBlueNZ

    Simple power supply questions

    That is not the best way to arrange the circuit. 1. The diode between the 5V power supply output and the main positive output will drop some voltage; this can be minimised by using a Schottky diode but it can't be eliminated. So if the adapter produces 5.0V the circuit might only receive 4.7V...
  15. KrisBlueNZ

    HP 1741A Oscilloscope

    OK, there's no need to replace that. If it wasn't working, you wouldn't get any high voltage.
  16. KrisBlueNZ

    HP 1741A Oscilloscope

    NTE287 is a replacement for MPSA42 so you should be able to do that. I doubt that either of them would cause that problem though. What do you mean by "HV Oscillator"?
  17. KrisBlueNZ

    HP 1741A Oscilloscope

    Bummer. You can put the original R13 back into the board. It's probably the CA3094A. At least, that seems the next logical suspect. Unfortunately, the CA3094A is obsolete. I found an eBay auction for five CA3094E devices, but you need the A suffix because the power supply is 30V and the...
  18. KrisBlueNZ

    Another treadmill problem

    Yes, a DC motor will turn backwards if the wires to it are reversed. The wires get in the way of seeing the board properly. Can you upload some pictures of the top side of the board with all the wires disconnected? Also, can you mark up the pictures to show where the motor connects, and where...
  19. KrisBlueNZ

    (woo woo) transformers 1:5 ratio - were to buy

    That doesn't disagree with my claims. I didn't, and don't, claim that it's impossible to convert energy from one form to another! These schemes all convert energy from one form to another. Light energy from the sun; wind which is created by heat from the sun; hydro which is created by...
  20. KrisBlueNZ

    HP 1741A Oscilloscope

    Ah, more progress! I'm not sure whether you need to change your resistor arrangement. As long as the ends are distant from each other, and the whole setup is not too far away from the board, and the wires are well insulated, you should be alright. I would expect the voltage at that test point...
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