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  1. Audioguru

    lithium polymer battery explosion

    Why isn't an old thread indicated with a red color or something that it is old? I rarely look at dates because most dates say "Today".
  2. Audioguru

    lithium polymer battery explosion

    New cells made at the same time are balanced when new. But they become unbalanced with age and use. If you have Lithium cells in series then you are supposed to use a balanced charger that automatically senses and adjusts the voltage on each cell. The balanced charger has a connection wire from...
  3. Audioguru

    Questions lithium polymer battery

    There is no way that an old Ni-Cad cell is 3.55V. Besides, a Ni-Cad cell could hold a charge for 2 months if you are lucky. I looked up the Sanyo battery number in Google and any battery retailers have lithium replacements.
  4. Audioguru

    The Dark Side

    I agree that the polarity of the capacitors is backwards. Here is a well-copied schematic on many internet sites showing NPN transistors and the supply voltage reversed. The capacitor polarity is correct but the circuit in the kit has the same polarity which is backwards.
  5. Audioguru

    Questions lithium polymer battery

    Just now, I entered here and saw the Batteryuniversity Warnings Table that I did not see yesterday so I went there. It gave me a warning that my pc has a virus and that that Norton (I don't have Norton) will delete all my files. Microsoft Defender anti-virus software that I use says my pc is...
  6. Audioguru

    Questions lithium polymer battery

    Turnigy is Hobby King junk from China. My friend bought 10 Turnigy batteries but only 2 of them worked. The newer Nanotech batteries are improved.
  7. Audioguru

    4011 IC

    The datasheet for a CD4093 shows that with a 5V supply, its input switches at a positive-going input of 2.2V minimum, 2.9V typically and 3.6V maximum. The switching voltage cannot be adjusted.
  8. Audioguru

    4011 IC

    You need a comparator IC (an LM393 is a dual comparator). It can be adjusted to switch at whatever voltage you want. you can add "hysteresis" to it so that it switches abruptly and quickly. You could also use a Cmos logic inverter or gate with a Schmitt Trigger input but you cannot adjust the...
  9. Audioguru

    Questions lithium polymer battery

    I told you that "It has been at half-charge for 22 years". Also it was never made too hot. Also it did not have thousands of charge-discharge cycles.
  10. Audioguru

    Questions lithium polymer battery

    I agree to store a Li-PO battery at 3.7V per cell. I store the Li-PO batteries for my RC airplanes at the half-charged voltage every winter and they last for years. I have the Li-ion battery from my daughter's first cell phone. It has been at half-charge for 22 years and still works fine.
  11. Audioguru

    Changing a positive and negative audio signal to positive only

    Audio is not DC, instead it is AC. So add a series coupling capacitor then bias the output to whatever voltage you want. Note that high levels still might produce some negative parts.
  12. Audioguru

    Need help understanding 70.7 Volt Line Audio

    Due to lots of negative feedback, a modern solid state audio amplifier has an output impedance of 0.04 ohms or less so that it can damp speaker resonances. But it feeds an 8 ohm speaker. Maximum power transfer is not even considered.
  13. Audioguru

    Need help understanding 70.7 Volt Line Audio

    There is no problem using an 8 ohm speaker on an amplifier rated for a 4 ohm speakers, the 8 ohm speaker will simply produce almost half the power which sounds only a little less loud. You needed to match the load only with antique vacuum tube amplifiers. Modern amplifiers that use transistors...
  14. Audioguru

    Need help understanding 70.7 Volt Line Audio

    Modern hifi amplifiers do not use an output transformer. They can drive an 8 ohm speaker or deliver almost twice the power into a 4 ohm speaker. The output of an amplifier does not want to see its rated full power load. In fact, with an output power less than full power its heating and...
  15. Audioguru

    Video signal amplifier.

    On my 37" diagonal HD TV I do not see any lines but if I get within 1' I can see the tiny pixels. On my 55" diagonal 4K TV I do not see any lines but if I get within 3" I can see the tiny pixels. 4K is awesome! I have been so close to the 4k screen watching a game all around me that I missed...
  16. Audioguru

    Video signal amplifier.

    On Black Friday I bought a wide screen "smart" TV from a grocery store (of course they normally do not sell TVs) for about half the normal cost. Also the tax was free and I got lots of "points" to get other goodies later. My cable TV provider charges a fortune for 4K reception and the smart part...
  17. Audioguru

    Need help identifying an electronic component

    It looks like a little transformer.
  18. Audioguru

    PAL vs NTSC?

    I have never seen NTSC beside PAL but if I did then the difference is so small that I probably would not see any difference. I have a 4k digital TV now and it is much better than antique NTSC or PAL.
  19. Audioguru

    Video signal amplifier.

    Hevans, Did you play with NTSC scrambled cable signals like I did? 1) They suppressed the sync but that was easy to fix. 2) They made the images negative at random that was also easy to fix. My circuit worked well but it was not automatic, I had to turn it on.
  20. Audioguru

    Momentary Switch to directional DC motor

    The "alternate action" circuit I posted is a simple flip-flop. The pushbutton only changes the forwards or reverse direction of the motor that runs continuously.
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