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  1. KrisBlueNZ

    Roland xp-50 keyboard problem

    Do you have a service manual? If so, please upload it somewhere - http://filemonkey.in or http://drive.google.com for example.
  2. KrisBlueNZ

    frequency feed through MUX

    Right, you can use a multiplexer with low ON-resistance and/or parallel two or more of them, to get a lower resistance. But if you're multiplexing between separate LC tank circuits, instead of switching just the inductor, the resistance is not so critical because it's not inside the tank...
  3. KrisBlueNZ

    Roland xp-50 keyboard problem

    Hi and welcome to Electronics Point :) I don't know what you mean by When the keyboard is dead, are all three voltages from the transformer present? Transformers often have thermal fuses to protect them against overheating, but they're normally one-time fuses; they don't normally reset when...
  4. KrisBlueNZ

    Voltage Multiplier Circuit Design

    Hello and welcome to Electronics Point :-) What are your component values? Especially, what is the capacitance of the capacitors? I assume your input frequency is 60 Hz? What kind of meter are you using to measure the output voltage?
  5. KrisBlueNZ

    Identifying transistor's PINs (Emitter and Collector)

    Data sheets are occasionally wrong, and transistors with the same part number from different manufacturers are occasionally different (or have been in the past), but I agree that data sheets are the first and most obvious source of information. At last, a real use for the transistor tester...
  6. KrisBlueNZ

    MPLAB very basic programming. Please help.

    In a C program, execution starts at main(). main() generally calls other lower-level functions, which call other lower-level functions, and so on. Some of these functions may be in the standard C library. Functions like sin(), printf(), malloc(), qsort() etc are part of the standard C library...
  7. KrisBlueNZ

    frequency feed through MUX

    As Harald says, a 555 is not designed to work with an LC circuit. You might be able to make it work (I've never heard of it being done) but you should use a circuit that's designed from the start to work with an LC tank. You can switch different inductors using a 74HC4051 but (a) the analogue...
  8. KrisBlueNZ

    pulse code modulation

    Your question is far too vague. 1. Posts in these forums are not text messages. You are allowed to use full words like "could", "the", "and" instead of "cud", "d" and "n". 2. Please give full part numbers for "ic7493" (do you mean the 74xx93 4-bit binary counter?) and "ic44233" (whatever that...
  9. KrisBlueNZ

    Motion sensor lighting with a difference

    Thanks for that. I think I get the idea. OK, that's different from how you explained it on the thread. The PWM fade-up/fade-down is pretty straightforward, although of course there are several options for how to do it. But I think we need to mainly focus on detecting the presence and absence...
  10. KrisBlueNZ

    Which voltage transformer for a laser printer

    Yes it's probably worth a try. Buy it from a retailer, not on eBay, so you have a warranty and some chance of getting a refund if it fails. I would replace the plug. Adapters are often unsafe. It also gives you an opportunity to check the thickness of the copper in the wires.
  11. KrisBlueNZ

    Identify This Please (May be a Heat High Limit)

    Because he wrote...
  12. KrisBlueNZ

    Identifying transistor's PINs (Emitter and Collector)

    Right. Or measuring current using a 10M current shunt resistor!
  13. KrisBlueNZ

    Next/previous switching a multiplexer

    You're right that the signal coming out a MIDI THRU connector will not be exactly the same as the signal going into the MIDI IN connector. Optocouplers introduce an effect called skew, because they respond more quickly to an active-going edge (a start bit or 0-bit in the data) at the LED than...
  14. KrisBlueNZ

    Identifying transistor's PINs (Emitter and Collector)

    This is why I suggested using a DMM on voltage range with 10M input resistance, back in post #2.
  15. KrisBlueNZ

    Advice identifying type of wire and sheath inside hair-curling tongs

    Looks like two layers of woven fibreglass "spaghetti" over standard twisted copper to me, but I'm no expert. Don't remove either layer, unless you want to void your fire insurance. People do leave these things switched on you know.
  16. KrisBlueNZ

    iPod as oscillator for scope wave learning?

    Good idea kpatz. I've suggeted this myself in the past. There's a free waveform editor called Audacity that runs on Linux and Windows, at least, that can generate waveforms and play them through the headphone output of a desktop computer or laptop. http://audacity.sourceforge.net
  17. KrisBlueNZ

    Identifying transistor's PINs (Emitter and Collector)

    Normally, you read the part number off the device, Google it, download the data sheet, and see which pin is what. If you can't find out that way, you can probably measure for Zener breakdown of the base-emitter junction. You need a DC voltage of at least 12V (from a power supply or a battery)...
  18. KrisBlueNZ

    iPod as oscillator for scope wave learning?

    Yes. You need two circuits to drive the base. A DC voltage, usually from a voltage divider made from two resistors, to set the bias for the transistor, and an AC (audio) signal, coupled onto the base via a capacitor. This audio signal comes from the iPod but the iPod's output level is too high...
  19. KrisBlueNZ

    iPod as oscillator for scope wave learning?

    Yes, an N2222 will work. Yes. Base bias is the current flowing into the base and out the emitter that causes the transistor to conduct slightly and pull its collector voltage down, to around half the supply voltage. Yes, it must be a DC current...
  20. KrisBlueNZ

    iPod as oscillator for scope wave learning?

    -3dB means that the amplitude of the audio signal encoded in the file is 3 dB less than the absolute maximum that can be encoded. Assuming the audio is processed at a resolution of 16 bits, the sample values that represent the waveform can range from -32768 to +32767; a range of 65536 (216)...
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