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  1. BobK

    Guitar Electronics .

    Unless the existing pots are dirty and operating sporadically, replacing them will not enhance the sound. If they are, cleaning them might help. Bob
  2. BobK

    741 Op-amp

    There are many versions of the 741. Exactly which one do you have? This might help with matching the pinout. Bob
  3. BobK

    Soldering station smoking problem?

    I have to ask. Are you sure there was not some packing material on the iron when you fired it up? Bob
  4. BobK

    Killing SSR (relays) - Need to understand

    I hope the wiring of the SSR is not as shown. Note that the AC voltage is going to one of the control inputs. Bob
  5. BobK

    How Do I regulate 3v DC?

    mA would be the right setting. If your meter has a separate jack for the positive probe for Amps, you would use that only on the A setting, not the mA setting. Perhaps this is why you are not getting a reading. Bob
  6. BobK

    Help to reduce this schematic price (beginner)

    This is why I said the 2nd order filter is more critical, it is harder to get the overlap right when the slope is steeper. Bob
  7. BobK

    Help to reduce this schematic price (beginner)

    I agree with gryd3 to go to a first order filter rather than second order. Not only for cost, but the components are less critical and it is likely to work better than a second order design unless you really know what you are doing. To save money, make your own inductors. They are nothing...
  8. BobK

    How Do I regulate 3v DC?

    DCA -> Direct Current Amps The meter probes have to be in series with the battery. If physically possible, have the battery part way out of the holder so that only the negative (flat) side of the battery is making contact. Then connect the red probe to the positive contact on the battery and...
  9. BobK

    Green LED power consumption

    A green LED with a Vf of 3.3V is likely a high power LED. Typical 20mA green LEDs run around 2.2V. If the battery starts at 3.4V and drops from there, the green LED will grow much dimmer as the battery depletes. Get a normal 2.2V green LED, a high brightness one if you want more brightness...
  10. BobK

    Apple vs the FBI

    I already covered that. It is a separate chip. From a teardown: Toshiba THGBX2G7B2JLA01 128 Gb (16 GB) NAND flash Bob
  11. BobK

    Apple vs the FBI

    Words like "Couldn't they", and "I presume" indicate speculation, not certainty. Do you have better information for us? Bob
  12. BobK

    Please help a newbie connect woofer

    Yes, because the bandpass is set at 3 octaves, it cannot handle 100 to 1000, only 100 to 800 (which is 3 octaves.) Choose the spread to be 10 3.4 Octaves, and it will allow it. Bob
  13. BobK

    555 PWM or is it?

    No, they are adjusting the duty cycle. The pot splits the charge and discharge times of the cycle, the two together add up to approximately the same period. Bob
  14. BobK

    Apple vs the FBI

    No, but if he steals the loaf of bread I will pursue him for the rest of my life. Inspector Javert
  15. BobK

    Please help a newbie connect woofer

    I played with the calculator a little. The bandpass gain is something they calculate and it only applies to second order or higher filters. It is not clear to me what it means. Higher order filters give sharper cutoffs, and therefore less overlap between the different drivers. Bob
  16. BobK

    Constant Current LED driver for "Varying Input Voltage"

    You can buy a constant current driver with those specs for a few bucks. And it will be switching, so no power dissipation problem. Bob
  17. BobK

    Apple vs the FBI

    The mod required is to the operating system. No one outside of Apple should have access to it, and, if it is like anyplace I have worked, only a limited number of programmers inside Apple would have access to it. Bob
  18. BobK

    Info for 2N3904 and 2N3906

    And complementary pairs are often used, surprise, as pairs! In a push-pull audio amplifier, the PNP conducts on the positive half of the signal and the NPN on the negative half. They are also used to form H-bridges and half bridges, which allow you for example, to reverse the current to a...
  19. BobK

    Frequency divider (less than 1MHz)

    A /D, FFT, DDS. In words: Convert to a digital signal, analyze the frequencies and phases using Fast Fourier Transform, divide the frequencies by 4, then use Direct Digital Synthesis to create the divided frequencies. I doubt that there is any simpler solution that would be practical. Bob
  20. BobK

    Kinetic Phone Charger

    Agree with Dorke, but, even with the circuit corrected, do expect a drop in voltage as soon as you connect a load. Bob
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