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  1. BobK

    Best course of action for high current DC supply

    This makes no sense. You are not going to have 300 to 600A going into or coming out of an 18650 cell. Bob
  2. BobK

    Woo-Woo Help please,

    Microphones do not make sounds. The induction loop you are referring to feeds audio electrically into a hearing aid. Are you wearing one when you hear this hum? Do your kids hear the hum? Assuming you are actually hearing something, practically any electric appliance running off line voltage...
  3. BobK

    convert 3v to 12v?

    The question is why you would want to use 12V for LEDs when the max voltage they require is about 3.5V? And what kind of power are we talking about? Bob
  4. BobK

    On/Off Speaker POP......but only on one channel

    A capacitor marked 220 is 22 pF, not 220. Bob
  5. BobK

    I think I'm starting a collection

    Hey, I've got an old bridge to sell you! It's in Brooklyn. Bob
  6. BobK

    Reversed Speakers

    Start from the right speaker. Follow the cable to the back of the receiver. Notice that it is plugged in to the output marked Left or L. Switch it with the cable coming from the left speaker. Or, just move the speaker on the right to the left and vice versa, without changing any connections...
  7. BobK

    Need help understanding 70.7 Volt Line Audio

    You are confusing two concepts. The max power theorem applies when a source has a high impedance, same order as the load. In a modern amplifer as @Audioguru has been saying, the output impedance is far lower than the max load impedance that it can drive. If you tried to connect a matching...
  8. BobK

    What did Santa bring you?

    Here is the small one I built on top of the full sized one. Excuse the messy workshop!
  9. BobK

    New project - 1967 oscilloscope restoration

    Hmm... Never seen a scope that did not have a DC input option, but you have found one! Bob
  10. BobK

    What did Santa bring you?

    @Harald Kapp, I did! Funny story about that. I got the skin off some grapes that grow in our yard with the powdery white stuff that I learned as yeast. I grew this for about 3 weeks, first just in water (the whole peel) then strained and adding flour, taking it through 5 or 6 feedings...
  11. BobK

    On a D.C. power supply.

    A computer supply will have the ground connected to the earth ground in its 3-prong plug. It then has voltages both positive and negative with respect to that ground. Bob
  12. BobK

    New project - 1967 oscilloscope restoration

    I think a DC offset in the vertical amp would do that, right? Is there possibly a trimmer to null the offset? Bob
  13. BobK

    New project - 1967 oscilloscope restoration

    So, what are you going to do with it now? Bob
  14. BobK

    New project - 1967 oscilloscope restoration

    Wow, impressive progress! Bob
  15. BobK

    On a D.C. power supply.

    The answer to your exact question is no. Whether or not the - terminal is considered ground depends on how you use the power supply. Suppose you have 2 12V power supplies and you want to power a circuit that needs + and - 12V. You will connect the + of one power supply to ground, and the -...
  16. BobK

    Looking for 60A 60V mosfet

    I get 740 matching results on Mouser when I search for N-charnnel MOSFETs with >= 60V Vds and >= 60A Id. It seems to me that one of these might be OK for you. Bob
  17. BobK

    PSU help please.

    Yes, that is correct. power supplies that have both voltage and current controls work in one of two ways. Some have a mode switch that you set to constant voltage or constant current. When in constant current mode, it adjusts the voltage to achieve that exact current. Others have a voltage...
  18. BobK

    PSU help please.

    You cannot. It is not possible to set both the voltage and current to a load. At any voltage it will draw a specific amount of current, To change the current, you must change the voltage. Bob
  19. BobK

    What did Santa bring you?

    Santa is literally feeding one of my other hobbies this year. Bob
  20. BobK

    How to determine current

    Do you have an idea of how long it ran on a charge of the battery? If so, divide 2000 by the run time in hours to get the approximate current in mA. Bob
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