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  1. audioguru2

    TV tx

    I don't know which TV system that transmitter works with.
  2. audioguru2

    TV tx

    This circuit can't be received by a normal TV. It is for the amateur radio microwave band. It dosn't have an input for sound. Its video seems to be FM modulated instead of AM modulated like broadcast TV. Good luck trying to find its weird ICs.
  3. audioguru2

    FM Transmitter

    Yes, but you would also need to build a receiver with the same frequency. I don't know what frequency they use. I don't think it is the 88Mhz to 108MHz FM broadcast band because in my area, all frequencies are used by radio stations.
  4. audioguru2

    FM Transmitter

    An FM radio, car radio or home stereo receiver can receive small FM transmitters well. Wireless intercoms and baby monitors have their own receivers that operate at frequencies different from the FM broadcast band. FM modulation is usually used since it avoids interference.
  5. audioguru2

    FM Transmitter

    A stable FM transmitter needs a voltage regulator and an RF output amplifier. For good sound it needs treble boost. A less complicated design won't be stable and won't sound good. It is difficult to find special parts for a radio receiver. Cheap kits were sold but worked very poorly. You can buy...
  6. audioguru2

    Step up 1.5v to 9v converter

    The TL499A works with a minimum of 1.1V supply, but then its output is only 60mW. 10mA at 6V, 20mA at 3V. It even has a series voltage regulator.
  7. audioguru2

    FM Transmitter

    Your coil is supposed to be close wound. Yours is way too open wound. Somebody had a transmitter like yours that didn't work. I built it and its frequency drifted all over when the battery voltage dropped, when the temperature changed and when something got near it or moved away from it. When...
  8. audioguru2

    FM Transmitter

    The coil is spread out way too much. The circuit operates at 100MHz where 5pF is a lot. Your breadboard has about 30pF between its tracks so won't work at such a high frequency. Use a pcb or Veroboard with very short traces and an FM radio to listen for it. Mine looks like this and works very well:
  9. audioguru2

    rf coil

    The datasheet for the 555 tells you how its monostable works: When pin 2 is triggered by the transistor driving it to ground, the 555's pin 7 reset transistor no longer grounds pin 7 so R3 charges C2 until its voltage reaches the threshold voltage of pin 6.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    Its output voltage (emitter of Q4) is 0.5V and also is ithe base of Q4. Therefore Q4 is shorted base to emitter. The output voltage of U2 is less than the output voltage when it should be about 1.4V higher, and it gets very hot. Therefore U2 is destroyed. Q2 might be damaged from being connected...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    If the collector and base of Q2 are reversed then the output of the project would be 33.3V and the output of U2 would normally go low to try correcting it. Q2, Q4 or both might be shorted.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    If U2 is faulty then the output voltage would be 34V minus two base-emitter drops. Measure the voltage at the output pin 6 of U2 to make sure. If the voltage is higher at Q2 then the transistors or one of them is shorted. Also, maybe U2 is destroyed by overheating. Check that the pins on the...
  13. audioguru2

    Wireless Intercom

    That transmitter is too simple. It doesn't have an input for audio to modulate it. It just transmits "silence". It is used to turn on and off a signal strength circuit that is connected to a radio receiver. The coil and capacitor's values determines its RF frequency. That site has many FM...
  14. audioguru2

    Wireless Intercom

    You could make an illegal radio station with a radio transmitter and a radio receiver. It might not be illegal in your country if you choose an approved frequency and a low transmitting power. The approved frequency might be crowded with other transmitters.The low power would limit its range...
  15. audioguru2

    Lowpass filter for subwoofer

    Hi Zak, Welcome to our forum. ;D The 22k pot is a dual pot. Maybe you found another problem with this project. I said it before about it: "This project's schematic, its parts list, its pcb layout and its photo don't agree with each other."
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    With R4 as 1k then the BZX85C will be fine. If R4 is reduced more then the zener will heat up and change its voltage, and U1 will get hot. Maybe the load drew too much current and the current regulation doesn't work. When the voltage from the current sensing resistor R7 exceeds the voltage from...
  17. audioguru2

    simple question about batt chargers

    Hi Walid, Rechargable batteries have different chemicals inside and need completely different charging circuits to match the type of chemicals. For some of the batteries, if it is fast-charged then a temperature sensor is recommended instead of a voltage sensor to stop charging, to avoid an...
  18. audioguru2

    HELP - resistors and dip-switch

    In the circuit you posted with the 555 and the opamp, replace R4 or R5 with your 10k thermistor. One position will make the fan speed up when the temperature is colder, so use the thermistor for the other resistor. Push the Quote button, delete text that you don't want in the quote then end the...
  19. audioguru2

    HELP - resistors and dip-switch

  20. audioguru2

    HELP - resistors and dip-switch

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