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  1. KrisBlueNZ

    Output of (voltage multiplier??) circuit

    Start by labelling all the nodes. Then draw the waveform at each node, including the DC offset. Nodes that are decoupled to 0V (the bottom line) with a capacitor can be assumed to be DC if there's no load, so you just need to calculate what voltage they will charge up to.
  2. KrisBlueNZ

    Heathkit IP20 Power Supply

    D'oh! You're right Trevor. That will be a problem. Thanks for catching that! Like you, I'm assuming that R23 is an NTC thermistor, attached to the output transistor heatsink. When the output transistors get too hot, its resistance will drop dramatically and it will draw more current and reduce...
  3. KrisBlueNZ

    Help on Sony video recorder GV-S50E

    Hi there Manel and welcome to Electronics Point :) Sorry about the slow response! I got a copy of the service manual from elektrotanya but it doesn't seem to have any information on the external charger. Please tell me if I'm missing something here. A rapid clicking sound from a switching...
  4. KrisBlueNZ

    Heathkit IP20 Power Supply

    I've redrawn enough of the circuit for it to make sense, and yes, I think you'll be fine with two 2N2955s. As duke37 suggested, you could get away with just one, but I guess you'll want it to look as original as possible. Edit: Or MJ2955s.
  5. KrisBlueNZ

    Issue with limiter pot inline with joystick pot

    Hi Gary and welcome to Electronics Point :-) Yes, that's going to happen. Think about it like this. Say your joystick potentiometer's resistance is 50 kΩ (and it has a linear law). Therefore at half position, its resistance will be 25 kΩ. Your controller will regard a 25 kΩ resistance as being...
  6. KrisBlueNZ

    Trouble Understanding The Schematics For ICL7106 Datasheet

    You're welcome. And that's a good tutorial you found there.
  7. KrisBlueNZ

    Trouble Understanding The Schematics For ICL7106 Datasheet

    Yes, they are using the two internal inverters in a standard CMOS oscillator configuration with one external resistor and one external capacitor, as shown in figure 9B on page 9. The external resistor and capacitor determine the frequency with moderate accuracy. The values suggested, 100 pF and...
  8. KrisBlueNZ

    Marshall AVT50 Guitar amp repair

    Hello Richard (or is it David?) I have no experience of that amp or that problem, but I do have the schematics. You can get them at http://elektrotanya.com/marshall_avt150_avt275.pdf/download.html. And they show that the headphone socket is driven separately from the main amplifier. So that...
  9. KrisBlueNZ

    Is it possible to connect one non-MIDI keyboard's sounds to another?

    Yes that should be possible. Each keyboard will have circuitry to generate the signal, and circuitry to amplify that signal to drive a speaker. You need to take the signal from keyboard #1 and feed it into the amplifier of keyboard #2 by mixing it with the signal generated internally in keyboard...
  10. KrisBlueNZ

    Triac question

    As I said in post #3:
  11. KrisBlueNZ

    Changing strobe pattern?

    Re my paragraph in post #12: That's not actually true - you don't need a T flip-flop between the oscillator and the first 4017's clock input, unless you want to guarantee that the gaps between the flashes are exactly the same duration as the flashes, i.e. a mark-to-space ratio of 1:1 or a duty...
  12. KrisBlueNZ

    Is there a MOSFET that turns OFF when voltage is applied to gate?

    Interesting! Depletion-mode MOSFETs rated for 500/1000V and up to 20A. Not relevant here, I don't think, but I'm sure they have some benefits for certain applications. Thanks for the info Adam :-)
  13. KrisBlueNZ

    Changing strobe pattern?

    It's an excellent example, I agree. If you or I were asked to produce a device to meet this requirement, we wouldn't consider doing it any other way. And we would "leverage" (yes, it's a verb now) that approach to add other advantages, and produce a wonderful product. But Peter is just starting...
  14. KrisBlueNZ

    Stage Line 500W amp repair project

    Hi again! Happy New Year and sorry for the delay. OK, I need some more voltages.
  15. KrisBlueNZ

    Is there a MOSFET that turns OFF when voltage is applied to gate?

    Check out this one: http://www.digikey.com/product-detail/en/SUP75P03-07-E3/SUP75P03-07-E3-ND/2623113 Very good specifications and nice and cheap. MOSFETs are not as robust as relays and need to be protected from various nasties that occur in the automotive environment. You can protect the...
  16. KrisBlueNZ

    Is there a MOSFET that turns OFF when voltage is applied to gate?

    There are JFETs that conduct by default unless reverse bias is applied to the gate, but 7A could be a problem for them. And there are P-channel MOSFETs that conduct when the gate is brought negative relative to the source, which is comparable to a PNP transistor. Why don't you post the circuit...
  17. KrisBlueNZ

    Changing strobe pattern?

    Is the idea to switch the oscillator between the two 4017s? It won't work as you've drawn it. You would need a latch to remember which 4017 the oscillator is to be directed to, and the Q9 outputs of the two 4017s would need to set and reset (respectively) that latch. You would also need a T...
  18. KrisBlueNZ

    Assistance with Transistor Theory

    OK. Can you answer these questions. Can you name any components (or subcircuits, for that matter) that you consider to be current-controlled? Is some base current, IBE, required to cause movement of electrons from the emitter into the base, where they can then be taken by the collector? If...
  19. KrisBlueNZ

    Changing strobe pattern?

    Right. You're right. All you're missing is that you didn't say how long you wanted the delay to be. I assumed you wanted a delay of one oscillator cycle, rather than zero cycles as in the design in post #1. If you want a longer delay, with the circuit we're running with now you have limited...
  20. KrisBlueNZ

    Sending Files Over the Internet

    Yes I had seen the dropbox etc suggestion; I was just pointing out that you can do it manually if you want to. I repeated the description of the automatic updates just to contrast the manual way with it.
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