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  1. KrisBlueNZ

    Capacitor discharges rapidly

    Also, what part numbers are the diodes? Is D1 a zener diode? And are D2 and D3 just normal diodes? The symbol you have used is not a diode or zener diode symbol.
  2. KrisBlueNZ

    Two inputs simultaneously

    Nice one Adam! If a bit of wasted current is not a problem, that's a nice solution!
  3. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    OK good. You had your meter set to the 20V range so it couldn't display voltages greater than 20V. Those voltages you're getting on C4 and C5 are low - they should be about ±50V - but let's worry about that later. Q519 and Q520 should have significant voltage on them. Q520 gets its voltage...
  4. KrisBlueNZ

    Find Fault in my built amplifier

    edit: This post has been copied from another thread because it (a) gives a readable circuit diagram, and (b) clearly outlines the shortcomings. -- (*Steve*) Yes. That circuit is a power amplifier. It accepts an input signal at "line level". This is also the signal level that a spring-line...
  5. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    No, measure ACROSS the two pins of TM403. Black probe to one pin, red probe to the other.
  6. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    Yes, AC. The voltage across the pins of TM403 comes from the secondary of the mains transformer so it will be AC. The other voltages will be DC though.
  7. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    That makes no sense. The amplifier would not work at all if there is no voltage across C4 and C5. How about the AC voltage between the two pins of TM403?
  8. KrisBlueNZ

    4-20mA using XTR111

    A current mirror is a circuit that accepts an input current and generates a corresponding output current. Both currents flow in the same direction - either "into" the mirror (for an NPN mirror, using conventional current) or "out of" the mirror (PNP mirror, conventional current). The current...
  9. KrisBlueNZ

    I2V Converter Circuit

    Hello and welcome to Electronics Point. This circuit will do what you ask for. If it's not suitable then you need to explain your requirements in much more detail.
  10. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    See if you can find where the wires from the mains transformer come onto the board. It will be near to the bridge rectifier. According to the schematic, there's a 2-pin connector called TM403 and another called TM401. Both pins of TM401 are the 0V rail. Connect your meter negative probe to that...
  11. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    Yes it looks OK. Try measuring the voltage of a battery.
  12. KrisBlueNZ

    Problem with Vintage Pioneer receiver SX-1000TW Output

    LOL cool :-)
  13. KrisBlueNZ

    DAC and ADC Simutaneous Testing

    If you are sending a 277-entry wave table to the DAC at a sampling rate of 12 MHz your sine wave frequency would be (12,000,000 / 277) = 43.321 kHz. Please explain yourself clearly.
  14. KrisBlueNZ

    DAC and ADC Simutaneous Testing

    Vary the rate at which you send numbers from your wave table to the DAC. If your wave table contains 277 samples, comprising one cycle of sine wave, and you are getting an output frequency of about 2.23 kHz, you must be transferring samples to the DAC at a rate of (2230 × 277) = 617.71 kHz...
  15. KrisBlueNZ

    Problem with Vintage Pioneer receiver SX-1000TW Output

    Ah, I see the reason. When you disconnect the wire from pin 7 of the power supply board, you disconnect the load (the amplifier output stage), but you also disconnect C12 and C13 (they're on the overview diagram - the first image in post #1 - in the bottom right area). These are the smoothing...
  16. KrisBlueNZ

    DAC and ADC Simutaneous Testing

    Sure, we can help you out. Which way did you come in? Here's a good source of answers to common electronics questions... The Internet! http://lmgtfy.com/?q=generate+sine+wave+using+DAC
  17. KrisBlueNZ

    Understanding Buck Converters

    It's probably best if you read some manufacturers' application notes. They are normally well written and easy to understand. And there are other sources of information on the Internet as well. But they are not all accurate and clearly explained.
  18. KrisBlueNZ

    Understanding Buck Converters

    Yes, that's fair. But, although it's true that feeding a PWM signal through a resistor into a capacitor will smooth it out, that's not a good analogy for the inductor. The inductor does things that a resistor couldn't even dream of doing!
  19. KrisBlueNZ

    Problem with Vintage Pioneer receiver SX-1000TW Output

    So it does. There is no explanation in the text for what the value in parentheses means. My guess is that it's the voltage with the amplifier driving a heavy load - for example, operating at the maximum rated output power of 50W into 8Ω per channel. If you want, try to duplicate the reading...
  20. KrisBlueNZ

    Understanding Buck Converters

    Kind of. It's definitely true that without the output capacitor, a buck converter won't work properly. I would describe it more as an energy converter, using an inductor. During the time that the switch (transistor, MOSFET, whatever) is ON, current flows from the input, through the switch...
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