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  1. audioguru2

    project help with toy IC boards

    I forgot. Disconnect the black speaker wire of the sound sources from the ground of the amplifier. maybe they have DC on them. Connect together the negative battery wires instead.
  2. audioguru2

    project help with toy IC boards

    Your sketches are good, but don't show how the 10k volume control pot is wired. I have sketched how it should look. The LM386 must have 0V on its input. The circuits are probably feeding DC to the pot and LM386. Therefore a 0.22uF input coupling capacitor is needed to feed audio to the pot and...
  3. audioguru2

    25v transformer to run 2 '200w' amps.

    About 1 week ago a guy on this site said his new Velleman amp blew up. On another electronics chat site we are joking about how weak it is because amps with similar power use paralleled output transistors to be reliable. Its distortion is listed at only 10W output. What about near full power? It...
  4. audioguru2

    What si that series resistor with Diode in and Inductor Switch circuit?

    When current is suddenly stopped to an inductor, the stored energy will try to keep the current flowing. Without a diode then there is nowhere for the current to go so the voltage goes very high. The diode conducts when the voltage tries to go high then the current keeps flowing until the...
  5. audioguru2

    project help with toy IC boards

    Just make a voltage divider with two resistors so the junction is 0.7V higher than the 3V output wanted. Then the transistor is an NPN and is connected as an emitter-follower with a 3V output when the 9V battery is new. A 2N4401 has high gain and a high max current. You don't sketch how you...
  6. audioguru2

    Audioguru FM Tx

    Transistors with the same part number have differences. Some are very good and others are not. There might be the same differences between two different RF transistors.
  7. audioguru2

    amplify..

    Instead of drawing a relay with a coil and contacts, you drew a box with 4 wires. So I don't know which wire does what. It looks like the transistor is giving the relay coil about 4V (maybe not enough voltage for a 6V relay), and the motor is fed 3V from the relay contacts. The relay coils...
  8. audioguru2

    25v transformer to run 2 '200w' amps.

    A 200W amp uses about 300VA from a power supply. It is probably rated as 200 Whats, which is about only 80 Watts to 100 Watts and uses 120VA to 150VA from a power supply. Are you making the Velleman amp kit that blows up? Two of them will draw a max of 240VA to 300VA from your transformer...
  9. audioguru2

    Infrared Receiver

    Don't you have modern TVs and VCRs and parts for them in South Africa? Don't people throw them away and you can remove their parts? Modern remotes send an IR beam in bursts of 38kHz pulses. The output of your filter will have 38kHz pulses with a high impedance. Do you have an oscilloscope or...
  10. audioguru2

    Audioguru FM Tx

    Harry's circuit has an extremly low level of 2nd and 3rd harmonics at 0.1% (-60dB). The oscillator and driver are emitter-followers and therefore produce a low output, too low to drive a class-C output transistor, so the output transistor has some bias to operate in class-B at a faily low level.
  11. audioguru2

    need help for cfl lighting

    The only way to reduce the battery current is to reduce the circuit's power output. That makes the light tube less bright.
  12. audioguru2

    Please help identify this logo!!

    It is Hirshmann or Hirshman or something like that. A similar connector was used on Norwegian intercoms made by Stentofon.
  13. audioguru2

    Audioguru FM Tx

    Yes, he will be very quiet if he is in a country without a justice system and the cops cut off his head or shot him.
  14. audioguru2

    Infrared Receiver

    Hi Axle, The filter is still part of your IR receiver so keep it in this same post. The 0.0001uF capacitor and 55k resistor make a highpass filter with a cutoff frequency of 29,090Hz when it has a very high impedance load. It is very simple so will have a very gradual cutoff slope, 14.5kHz will...
  15. audioguru2

    project help with toy IC boards

    If you don't want to use an LM317L voltage regulator, you could make a voltage divider with two resistors then use a transistor as an emitter-follower to buffer the voltage and feed it to the 3V chip. The resulting 3V won't be regulated so it will drop as the voltage from the battery drops, but...
  16. audioguru2

    Infrared Receiver

    Now all that is needed to extend the range is to cover the photodiode with undeveloped film or something else to block visible light but pass IR, then make a tuned amplifier that is tuned to the frequency of the carrier of the remote. Rectify the received, filtered and amplified signal and use...
  17. audioguru2

    Audioguru FM Tx

    Sssaaa got caught by the RF cops for causing interference. He is in jail waiting for somebody to bail him out. ;D
  18. audioguru2

    RC-(remote controlled) Car

    Your varactor diodes have +9V on their anodes and ground on their cathodes. They are forward biased. Turn them around.
  19. audioguru2

    Audioguru FM Tx

    The circuit's designer is responsible to bail users out of the jail that the RF cops use. :o
  20. audioguru2

    Audioguru FM Tx

    Why not use the FM stereo transmitter IC circuit that is used in all the MP3 to car radio products and add the RF amplifier to it. Then everybody who makes and uses it will be arrested by the RF cops.
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