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  1. Audioguru

    Car Radio Overheats, sound go out. Second radio same problem. Need help

    An amplifier overheats if its output is shorted or if the output of one channel is shorted to the output of another channel. Most car radios use 4 ohm speakers, maybe yours is overloaded with too many speakers or 2 ohm speakers. Maybe the original wiring had one terminal of each speaker...
  2. Audioguru

    Idle current set

    Positive on MP701 and negative on MP702 with no signal and the multimeter set to measure DC volts. 13mV on two series 0.47 ohm resistors is a current of 13.8mA. Is the amplifier rated at 20 real Watts into 8 ohms per channel? It might say 40W to 60W max or peak.
  3. Audioguru

    Electrolytic capacitors: Opinion required please

    I used 450V capacitors with vacuum tubes 55 years ago. Maybe the replacement capacitor was old and in storage so long that it lost its "forming". I looked up forming and it said a very high current could flow causing heating of the chemicals inside causing gasses inside to cause an explosion...
  4. Audioguru

    How is this hobby cannon made?

    What is the white-hot wire from? What explosive material? Gunpowder?
  5. Audioguru

    Led Timer Circuit

    I have two circuits that came in cheap items from The Dollar Store. They have a red and a blue LED and when shaked they quickly flash the red then switch to quickly flashing the blue exactly 32 times for each pair then it turns off. I replaced the shaker switch with a pushbutton switch. Each...
  6. Audioguru

    Electret microphone is giving unsual resistance

    Try it first without stretching the duration of pulses. If you do not use it in a location that has echos and noise then it might work fine. My daughter bought a cheap Chinese clap switch then asked me if I could stop it from quickly turning off the thing it turns on. It detected the echo of a...
  7. Audioguru

    Spark gap transmitter

    Does anybody still listen to the snap, crackle and pop of AM radio anymore? My FM radios do not produce the severe AM interference even in a lightning storm. Oh yeah, I forgot that airplane and control tower communications use AM so a pilot can "break in" and holler "MAYDAY, all engines have...
  8. Audioguru

    Electret microphone is giving unsual resistance

    You must deactivate the unused flip-flop so that it does not cause interference to the main flip-flop and so it does not become damaged by static electricity. If you let the pulse from a clap have a short duration then an echo or other sound will reset the switch when you do not want it to...
  9. Audioguru

    Question about A/C electricity

    The motors shown in the photos look like small brushless hobby motors that have 3 wires, one wire for each phase of the AC. It looks like the motor in the second photo is a generator driving an LED and looks the same as motor talked about and driven as a windmill generator on another website.
  10. Audioguru

    Electret microphone is giving unsual resistance

    The CD4027 is a dual flip-flop. Deactivation of the second flip-flop by grounding its clock input and connecting the other inputs like the first flip-flop is not shown, to prevent interference. A longer duration of the pulse from the opamp is needed to prevent an echo or other sound from...
  11. Audioguru

    I need input on how to build a voltage supply circuit for LEDs using wind power.

    The voltage and current from the generator varies so much that the LEDs will be a little dim and bright. If you plan to have the LEDs light fairly well only when the generator output voltage is 15V to 24V then three 2V red LEDs and a 910 ohm series resistor lights them with 19.8mA or 19.1mA when...
  12. Audioguru

    I need input on how to build a voltage supply circuit for LEDs using wind power.

    LEDs have different forward voltages even if they have the same part number. When you parallel LEDs then their forward voltages all must match. In parallel the one with the lowest voltage lights well and the others either do not light or light dimly and the LED with the lowest voltage takes most...
  13. Audioguru

    1960? B.C. (before cassettes)...

    Google lists Wikipedia and others with history of the compact tape cassette and the competitors Telefunken and Grundig. I think there was also a Japanese one or two. Philips won. I worked in a Philips car radio factory when they developed their tape cassette player that replaced an 8-track tape...
  14. Audioguru

    Motor control 3.7v

    The MCU does not produce enough output current to cause the transistor to saturate. Motor speed controls for low voltage RC airplanes and low voltage RC drones use low voltage Mosfets that use a very low input current and a very low voltage loss when they turn on. Ordinary Mosfets need an input...
  15. Audioguru

    LED strips underwater

    Correct. You can simply measure the resistance of water with a multimeter. The area of the probes and distance apart affects the resistance.
  16. Audioguru

    Motor control 3.7v

    The 2SD313 Oriental transistor has a maximum saturation voltage loss of 1V when its Ic is 2A and its Ib is 200mA. Your Ib is probably a lot less than 200mA.
  17. Audioguru

    How can one regulates DC voltage automatically to the voltage required by an appliance using micro-c

    All my appliances use AC. My AC voltage is very reliable and is regulated very well by my electrical utility company. I wonder which appliances in Nigeria use DC and why do they use different voltages? Then later he says he wants an inverter to feed a regulated DC voltage to electronics? I use...
  18. Audioguru

    What type of battery is good for emergency power for blackouts?

    Many people live in high rise apartment buildings that have a single elevator and no generator. They complain to TV news that they are stranded when it takes a week or more to replace the worn out elevator or there is an electricity blackout and they are in a wheelchair. People complain about...
  19. Audioguru

    LED strips underwater

    I think a few thousand volts on high surface area probes in salt water is pretty close to a short circuit.
  20. Audioguru

    LED strips underwater

    Pure water is an insulator. Tap water conducts a little. Salt water conducts more but is far from a short circuit.
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