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  1. KrisBlueNZ

    IH5011 Fet switch , virtual ground switch?

    Most semiconductors, like transistors, MOSFETs etc, are controlled by a voltage or current between two specific pins. Transistors respond to base-emitter current; MOSFETs respond to gate-source voltage. But JFETs are different. The source and drain are just opposite ends of a symmetrical area...
  2. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    Did you connect the black lead of the multimeter to pin 4 of N502 (or something that is connected to it)? That voltage should definitely be positive!
  3. KrisBlueNZ

    does this seem right?

    The pullup resistors are needed because the LM339 has open-collector outputs that pull low but don't pull high. I wouldn't use that design - not at 12V, anyway. As the LM339 outputs are transitioning from 0V to 12V or from 12V to 0V, there will be a point where both MOSFETs are ON...
  4. KrisBlueNZ

    Will an AOC - 23.6" LED HD Monitor work with my OLD PC?

    I already found the right one. It doesn't have information on the video resolution.
  5. KrisBlueNZ

    Will an AOC - 23.6" LED HD Monitor work with my OLD PC?

    Yeah, that's the one I found too. But that's for the 745 model, and according to post #1, you have a GX620. Or am I missing something?
  6. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    OK, sorry, I made a mistake with the voltages I listed in post #6. The 3.24V that you measured is the right voltage to make the power supply start up. So the problem is not in the crowbar circuit. So there's no need to add the 1k resistor. When you have around 3.24V on the junction of N505 and...
  7. KrisBlueNZ

    Sense sound and fade LED

    OK, I'm not sure that CR2032s are suitable. Could you use alkaline AAA cells? If so, how many could you fit? What's your budget? What colour LEDs? Do you have an idea of how bright you need them to be? Edit: How are you planning on building the circuit? Do you intend to make a printed...
  8. KrisBlueNZ

    Sense sound and fade LED

    Hi there and welcome to Electronics Point :-) Yes, that should be possible. What kind of batteries are you considering? How many LEDs? What battery life do you need?
  9. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    Right. That schematic looks like it matches the one in the service manual. You said there "appears to be" 3V on pin 13. Are you sure? That's the pin that controls whether the other power rails are enabled or not. If there's 3V on it, and the other rails are not present, that indicates a problem...
  10. KrisBlueNZ

    In rush chokes on op amp inputs

    15 µH is a pretty low inductance. What's the frequency of the signal the circuit is monitoring? The inductors could just be for RF rejection or to stop the circuit from responding to very short transients or noise bursts.
  11. KrisBlueNZ

    check the circuit

    I couldn't find a modulo N down-counter but I did find two good articles that explain enough for you to be able to design one. First, Tony R. Kuphaldt's excellent lessons at http://www.allaboutcircuits.com/vol_4/chpt_11/3.html. This section on digital logic is also available for download as...
  12. KrisBlueNZ

    check the circuit

    OK. and there's no need to call me sir :-)
  13. KrisBlueNZ

    check the circuit

    I don't understand what you want. Do you want a schematic for a mod 5 down counter? You can probably find one using Google.
  14. KrisBlueNZ

    12V - 350V 200mA converter for motorcycle CDI

    (Oops - I wrote this earlier but didn't click Send. Steve, you've already asked the question, but I've tried to explain it in more detail.) Re the traces in post #85, you need to set the oscilloscope to differential mode, so it displays the difference between the two input signals. This may be...
  15. KrisBlueNZ

    check the circuit

    I have no idea what you mean by that. Do you mean 7 - 5 = 2? Because 7/5 is 1.4. And in any case, a 3-bit counter has eight states, not seven. Right. Right. In an up-counter, when the count tries to increase from the maximum count, it resets to 0, yes. In a down-counter, when the count tries...
  16. KrisBlueNZ

    IH5011 Fet switch , virtual ground switch?

    For the benefit of anyone else reading this thread, here are the three pages of the data sheet: I haven't seen this type of device before, so I'll have to make some guesses and assumptions. It looks like each element is a P-channel JFET, and a diode. A P-channel JFET is turned OFF by...
  17. KrisBlueNZ

    PSP 3000 - putting back dat screw...

    Hi there and welcome to Electronics Point :-) Sounds like the "can of worms paradox" has bitten you :-) There are two likely reasons. First, the screws are different lengths and you need a long one for that hole, but you've put a long one into a short hole, so you're left with a short screw...
  18. KrisBlueNZ

    Help, transistor circuit not working

    Hi Scuba_steve and welcome to Electronics Point :-) Thanks for giving us full information on the LED drivers you're using. The LDD-1500L can draw up to 1.5 amps. The 2N3904 is rated for a maximum collector-emitter current of only 0.2 amps. You'll have to use something different. I recommend...
  19. KrisBlueNZ

    check the circuit

    Mod 5 means that there are five possible output values, and because it's a down-counter, they will be generated in descending order. Specifically, mod 5 means "the remainder after division by 5". If you divide any number by 5 and look at the remainder, it will always be either 0, 1, 2, 3 or 4...
  20. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    OK, it's a Chinese LCD TV. See http://www.cnet.com/products/dynex-dx-l42-10a/specs/ The service manual is available on elektrotanya.com but it's 100 MB. The 5V rail is provided by an always-ON power converter using T501. The main board sends a control signal called POWER to the power supply...
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