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  1. KrisBlueNZ

    New (well back into) the game

    Hi Colin and welcome to Electronics Point :-) Thanks for the introduction.
  2. KrisBlueNZ

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

    OK, it looks like the whole negative rail is missing. Can you find C4 and C5? These will be huge cylindrical electrolytics. I think they're the big black things at the left of the last pic you posted. Can you measure the positive terminal of C4. It should be around 40~50V positive. Then the...
  3. KrisBlueNZ

    Wall adapter voltage issue

    Not likely to be a problem. Which model Arduino are you using? Can you post a link to the technical information for it?
  4. KrisBlueNZ

    Wall adapter voltage issue

    That is normal for the old type of adapter that uses a heavy transformer that steps down the AC mains voltage directly. These adapters don't have any regulation, so the output voltage varies quite a lot depending on the load current. The marked output voltage applies when the maximum rated...
  5. KrisBlueNZ

    Problem with Vintage Pioneer receiver SX-1000TW Output

    OK, here are the specs for the 2SC793 output transistor. Silicon NPN in TO-3 package. VCBO = 100V; VCEO = 80V. IC max = 7A; PD max = 60W fT = 9 MHz hFE 30~200 at IC = 1A and VCE = 5V Digikey have the ON Semiconductor 2N3442G: 140V 10A USD 2.85...
  6. KrisBlueNZ

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

    OK, those "1." indications are because the voltage is too high for the range you selected. If you see that indication, you need to use a higher voltage range. Just for future reference. OK, there's no significant voltage on Q520. The voltages you listed for Q520 are negative voltages, right...
  7. KrisBlueNZ

    Problem with Vintage Pioneer receiver SX-1000TW Output

    You're right. Having Q801 completely shorted out wouldn't cause the fuse to blow. The DC conditions at that part of the circuit cannot affect the output stage. It would have just stopped any signal from getting through. You're also right that the most likely cause of fuse blowing is failed...
  8. KrisBlueNZ

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

    Yes, always measure relative to the 0V rail unless you're measuring "between" two specified points. What is that 4-pin connector with the wire pulled out of it? And the other connector, is the wire properly seated in it?
  9. KrisBlueNZ

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

    That's definitely a bad sign! But let's investigate the other problem first, because a missing supply rail could cause the other problem. Can you find Q519 and Q520? They are probably power transistors and they may be mounted on heatsinks. I don't know which board they're on - the diagrams in...
  10. KrisBlueNZ

    4-20mA using XTR111

    It works. I simulated it. The two 120k resistors across a 4V supply are equivalent to a 60k resistor to a 2V supply (see Thevenin equivalent on Wikipedia for more information). A non-inverting amplifier with 4k feedback resistor and 60k to ground has a gain of 64/60 or 1.06666667. If you...
  11. KrisBlueNZ

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

    OK, find R954 on that circuit board and measure the voltage at each end, with your black meter probe still connected to the 0V rail (chassis or outer metal of the RCA connectors). Also tell me whether it is getting hot. (Touch it quickly at first - it could be very hot, and you don't want to...
  12. KrisBlueNZ

    Transmit and receive parallel data through radio link

    OK, here we go. The transmitter and receiver are independent but I've shown them both on the same timing diagram for convenience, with the transmitter's signals at the top and the receiver's signals at the bottom, and the transmitted data stream in the middle, labelled TXD and RXD straddling...
  13. KrisBlueNZ

    4-20mA using XTR111

    That circuit is not a differential amplifier. It has only one input, which is referenced to the 0V rail. That means it is single-ended, not differential. I assume you can't control the output voltage range from the ADC? You can't modify the controller to use a different output voltage range?
  14. KrisBlueNZ

    4-20mA using XTR111

    1. Yes. 2. No. A voltage divider will reduce a voltage range but it cannot expand a voltage range. You have a voltage range of (2.0 - 0.5) which is 1.5V and you want a voltage range of (2.0 - 0.4) which is 1.6V. This requires gain. A voltage divider cannot do this. If you put your 0.5V~2.0V...
  15. KrisBlueNZ

    Finally got me a 'scope - Have some questions

    Probably just Google test equipment suppliers in your state or city. Any company that sells oscilloscopes will sell probes separately, and will sell good quality probes, because anyone who buys an oscilloscope and gets crappy probes would be very unhappy and would come straight back. Not like...
  16. KrisBlueNZ

    4-20mA using XTR111

    Here's what I suggest. I don't have much experience with instrumentation so someone else may be able to suggest some improvements, but this is the basic idea. This is a non-inverting amplifier based on a Texas Instruments OPA376 op-amp. It has a gain of ((2 - 0.4) / (2 - 0.5)) and a fixed...
  17. KrisBlueNZ

    4-20mA using XTR111

    http://www.ti.com/lit/ds/symlink/xtr111.pdf So you have a signal that ranges from 0.5V to 2V and you want to feed it into an XTR111 and get an output current of 4~20 mA, is that right?
  18. KrisBlueNZ

    parallel voltage source

    Yes that circuit will work. An input voltage range of 0~5V will produce an output voltage range of 1~5V. If this question relates to your other thread at https://www.electronicspoint.com/threads/4-20ma-using-xtr111.269944/ then don't worry; I'm working on a solution for your question.
  19. KrisBlueNZ

    Finally got me a 'scope - Have some questions

    I tried Googling Leader 8060 oscilloscope user manual and found a link to a manual for the 8050 model which is similar: http://www.tequipment.net/pdf/Leader/LS8050_manual.pdf. If you try a bit harder than I did, you might find the right one. I wouldn't touch them with a ten foot pole...
  20. KrisBlueNZ

    machine language to assembly language

    That's right. All of those numbers are in hex. The 0000, 0002, 0004 etc are the memory addresses where those bytes will be placed.
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