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  1. KrisBlueNZ

    BASIC LED project - help/advice required

    Hi there and welcome to Electronics Point :-) There are two ways to drive the LEDs: directly, or using a boost converter. A boost converter requires an inductor and generates a higher voltage than the battery voltage, so multiple LEDs can be connected in a string that adds up to more than...
  2. KrisBlueNZ

    8-Bit Music

    Try Googling portable soundboard. Or you could make your own with a microcontroller. I would go for one with a DAC - 10 bits at least, preferably 12. You can use an SD or Micro SD card for the audio, but you'll need code to interpret the file system. Edit: You can probably find everything you...
  3. KrisBlueNZ

    Need help to understand circuit!!

    Great answer kpatz! Yes, the pullups are inside the micro. The P89V51RD2 from NXP is an 80C51 device, so it uses "quasi-bidirectional" I/O for all its digital I/O ports except Port 0. Each quasi-bidirectional port has only a single register in the SFR space; for each bit, writing a 0 makes the...
  4. KrisBlueNZ

    Modifiying timer circut for lower voltage

    Good answer Dan. For clarity, the "time the output will be high" is the time between beeps, and the "time it will be low" is the duration of the beep. The times are measured in seconds, and as you pointed out, resistances are in ohms and capacitances are in farads. R1 (4.7 megohms) is...
  5. KrisBlueNZ

    Oscilloscope calibration

    Great advice Steve!
  6. KrisBlueNZ

    Split Rail Power Supply

    Are you after a supply voltage splitter with 1A output capability? This would be a circuit that you connect to a DC power source, say between 6V and 35V, and it will provide a "half way between" output that becomes your 0V rail, while the positive and negative connections from your input source...
  7. KrisBlueNZ

    Help with Landline telephone

    Could be several things. 1. It could be something else connected to the line. Either try a different phone in the same socket, or take that phone to someone else's house and try it there. Just to confirm the problem is in that phone. 2. Take some photos of the inside of the phone. Include a...
  8. KrisBlueNZ

    power board - don't know what to try

    Hi sparkmonkey :-) It's nice to see you wanting to fix the board instead of throwing the whole thing away. I think we have enough e-waste already! Another thing that's probably worth checking is the diodes in the live section. In the picture in your first post, these diodes are the one next...
  9. KrisBlueNZ

    do you know these resistors?

    Cool :-)
  10. KrisBlueNZ

    Attempting vintage receiver repair - Please Help!

    You must have done more than that. Connecting the positive and negative probes to any different points in the circuit won't cause any damage (unless the multimeter is on a current range). Did you touch one of the probes to two different parts of the circuit at once? If there's a mains voltage...
  11. KrisBlueNZ

    Mapper

    That's a good start, but not all of the circuit is visible. GIF is a better format than BMP for schematics - the cropped GIF in this post is only one tenth of the file size of the BMP. I see you reduced your screen capture to a monochrome image to make the file smaller. That's a good idea, but...
  12. KrisBlueNZ

    Attempting vintage receiver repair - Please Help!

    OK, thanks for the photos. They're a good start. You've probably figured this out already, but... The board between the electrolytics is the power amplifier, with the output transistors mounted on the back panel and connected with wires. The board on the underside in front of the mains...
  13. KrisBlueNZ

    m16 halogen socket replacement and questionable wire

    Hello and welcome to Electronics Point :-) Please upload a photograph or two. Each photo should be in JPG format and up to 140 kilobytes in size. Click "Go Advanced", then click the paper clip icon. Click Browse and select the image file. Repeat for any other images. Click Upload. When the...
  14. KrisBlueNZ

    Eye Movement Desensitization Rehabilitation device

    Good one!
  15. KrisBlueNZ

    Mapper

    brevor, why don't you post the schematic here. It may be useful to others, and we can check it. I'm interested to see it too. I've started designing a circuit but it has a lot more than eight parts. Click Go Advanced, then click the paper clip icon. Browse and select the file, click Upload.
  16. KrisBlueNZ

    do you know these resistors?

    OK. I think R7 should be about 560 ohms, for example http://www.digikey.com/product-detail/en/CFR-50JB-52-560R/560H-ND or http://uk.farnell.com/welwyn/mfr4-560rfi/resistor-metal-film-560-ohm-500mw/dp/1833360 and R1 should be about 330 ohms 0.5W fusible - for example...
  17. KrisBlueNZ

    Attempting vintage receiver repair - Please Help!

    Pictures would be useful. One from above, showing the whole thing, then two of the circuit board - one from above and one from below. If there's no signal coming through, just a hum, this could mean that the output stages of the amplifiers have failed and slammed against the positive supply...
  18. KrisBlueNZ

    Circuit board problem

    That circuit board looks like a stereo audio amplifier. But you said you were repairing a convergence board from a TV. You have now highlighted two rows of pins which don't seem to show any "gold coloured part" that "fell off" while you were pushing a pin through the board. You've also...
  19. KrisBlueNZ

    PIC not working

    I don't understand what you mean. Run the PIC from a crystal, send the CLKOUT signal from the PIC to the SPI clock input of the same PIC? What incoming frequency are you talking about?
  20. KrisBlueNZ

    PIC not working

    Hi ami85t I have been looking at your C-to-asm conversion of the Picodetector code. As you know, the Picodetector uses a PIC whose clock frequency varies depending on the resonant frequency of an LC circuit. The PIC is deliberately reset at regular intervals by a watchdog timeout, and it...
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