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  1. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Those are two other resistors that Chaggy78 wants to replace. They were mounted raised off the board, and were visibly flaking due to long term overheating. They are marked 620 ohms 5%. My guess is that they're wirewound, 2W or 3W rated. I'm suggesting something like the Vishay BC AC04 series...
  2. KrisBlueNZ

    LED VU meter with transistors, dotted...

    You can also use the LM3915. That transistor-based circuit has a linear response, like the LM3914, and unlike the LM3915 and LM3916, which have a logarithmic response and are designed for audio level monitoring. It's possible to change that design to a dot graph but it is not well designed and...
  3. KrisBlueNZ

    Pickup Winder Build

    Your speed controller is designed to be powered from 12~24V but you're using a 5v power supply with it? Can you post part numbers and links to data sheets or catalogue pages for your power supply, your speed controller, and your motor? What is the actual problem? The motor doesn't turn when...
  4. KrisBlueNZ

    12V Incand Desk Lamp - Retrofit with LED

    If you're running the LED at 60 mA, a 1000 uF smoothing capacitor (rated at 25V) will be fine. This will be an electrolytic capacitor. The amount of smoothing determines how much the DC voltage "dips" in between mains voltage cycles. When AC mains is full-wave-rectified and smoothed, the...
  5. KrisBlueNZ

    6 Buzzer Project

    You would have saved time if you had said so before. That Google search found a page http://www.satsleuth.com/schematics.htm which has links to several relevant designs: http://www.techlib.com/electronics/games.html http://www.desmith.net/NMdS/Electronics/Jeopardy.html...
  6. KrisBlueNZ

    Skeleton Potentiometer

    Nice pictures Ray, but as you said, they don't reveal much, except that the instrument cluster is beautifully made and in very good condition. OK, so you want to go for the fixed resistor option. That should be OK. Personally I would have tried to replace the trimpot first, and only use the...
  7. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    Well done! Thanks for your kind words.
  8. KrisBlueNZ

    Rasberry Pi + Relay

    That looks good.
  9. KrisBlueNZ

    6 Buzzer Project

    Have you looked here?
  10. KrisBlueNZ

    Skeleton Potentiometer

    Hi Ray. Let's start from the beginning. Correct me if I'm wrong on any of these. Your fuel gauge (and the related low fuel light) are erratic because of intermittent behaviour of the trimpot you've shown in the photo. The tank level is sensed by a tubular sender with a float and resistance...
  11. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    OK. I agree you should increase the 100 ohm from the shutdown pin to 0V. I would increase it significantly, say to 220 ohms.
  12. KrisBlueNZ

    Add a switch to an AC/DC power supply?

    I see. We thought the cylinder was in the "line" between the mains plug and the power supply, but it's actually a plug-in adapter and the cylinder is in the DC cable. The cylinder is a ferrite interference suppressor. You can insert a switch on either side of it, whichever you prefer...
  13. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    OK that's a good start. To really understand the design, I would need a complete schematic diagram of the PCB and the off-board components it connects to. The ICs need to be represented as rectangles, apart from the LM324 which needs to be represented as four op-amp symbols (see the data sheet...
  14. KrisBlueNZ

    Add a switch to an AC/DC power supply?

    The cylinder is probably a ferrite filter to reduce interference conducted back into the mains supply. If that's what it is, you can put the switch on either side of it. Upload a photo. See https://www.electronicspoint.com/attaching-images-t250594.html
  15. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    OK. Can you also post some photos of it? The inside of the whole unit, viewed from above and below, and a close-up of the main circuit board, from above and below, could be very helpful. Use natural light if possible, and take the photos looking straight down or at a slight angle. If there's...
  16. KrisBlueNZ

    Sorting things out with a small circuit

    All three of those regulators are adjustable. One of the pins is probably used to adjust the output voltage. Download the datasheets. They will have a sample circuit diagram for a typical application. I said that almost all regulators NEED bypass capacitors, so no, you can't complete the...
  17. KrisBlueNZ

    Sorting things out with a small circuit

    Nearly all regulators need decoupling capacitors across the input and output, for stability. Look at the 7805 data sheet. I would stick with a 6V battery and an LDO. Less heat, less power wasted, more standard battery, smaller. Suitable LDOs aren't THAT expensive. Definitely cheaper than an...
  18. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    Have you searched for information about the inverter? It's possible (but unlikely) that a schematic might be available online, or there might be notes on other faults and repairs. What is the brand and model number? Thanks for the description of your repairs so far. I would like to know about...
  19. KrisBlueNZ

    Rasberry Pi + Relay

    Sorry, I must have missed your post #5. That page with the I/O connector pinouts is excellent. It doesn't say anything about the JD-VCC jumper though. It looks like there's 5V available on the I/O connector regardless of the jumper position. That Sainsmart board needs 15~20 mA drive current...
  20. KrisBlueNZ

    Comparator inputs

    You're welcome :-) I enjoy helping, especially on projects that I find interesting. I mentioned Skype because I think I will need to be involved during testing and debugging. As you said, this is not a trivial circuit, and getting it running properly will not be trivial. Communicating by posts...
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