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  1. Audioguru

    Led stair lights with 2 motion sensor. circuit help!

    An LDR detects light but you said your stairs are dark so it cannot be used. A motion detector can also use infrared light (that is invisible) to detect motion. The infrared light is on all the time so it uses some electricity all the time but it can be pulsed to reduce its power. You probably...
  2. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    Did you measure the resistance of the solenoid coil plus the resistance of your meter's leads?
  3. Audioguru

    how can i adjust the Av gain of this amplifier from 12 to 10, the AC signal is 10mV, 1kHz,

    hfe is AC current gain and has almost nothing to do with a transistor's voltage gain. The BC108 is very old and is not made anymore. A BC547 uses the same chip but in an epoxy package. A BC547B is a typical one and my new simulation uses it. The voltage gain of a transistor with no additional...
  4. Audioguru

    how can i adjust the Av gain of this amplifier from 12 to 10, the AC signal is 10mV, 1kHz,

    The voltage gain is not 12 times, my simulation and calculation including the emitter resistance inside the transistor is a gain of about 11.5 times but the 830 ohms is not a standard resistor value. I used 1k ohms to replace the 830 ohms and got a voltage gain of about 9.5 times. Add 20k...
  5. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    Is the original circuit made on a compact printed circuit board but you made yours on a solderless breadboard with messy wires all over the place?
  6. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    You replaced one Mosfet on an original board with one of the Mosfets from Digikey and it worked fine. But 12 Mosfets from Digikey burned up in your circuit. Then something is wrong with your circuit, not the Mosfets. Maybe there is a different set of solenoids? Try your circuit driving the...
  7. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    An old 7404 TTL IC with a minimum output high of only 2.4V is completely different to a modern 74HC04 or 74ACT04 which are Cmos and have outputs that go up to the supply voltage. The IRL540 that overheated was either defective or it was an IRF540 marked wrong.
  8. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    The Mosfets that were burning up were probably cheap Chinese fake ones from ebay.
  9. Audioguru

    Old Resistors

    I listened to The Fixed Stars, The Frontier To The Beyond and it was wonderful to hear. I didn't have some crystal wine glasses handy so I didn't try to play it which would have driven me MAD!
  10. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    No Way! A lousy old 7404 output high is 2.4V minimum, no where near 5V. You need a 74HC04 which is high speed Cmos and its output goes up to its supply voltage. EDIT: You said 7404 and you also said 74HCT04 which is high speed Cmos with an output that goes up to its supply voltage. Which is it?
  11. Audioguru

    TDA7297 cascade channels?

    You said the 1972 car radio was mono. In 1972 I worked for Philips car radio engineering. All the AM/FM car radios we made were stereo, not mono. The cheap AM-only radios were mono. You said you are taking the audio from the tap on the radio's volume control which has reduced levels of mid and...
  12. Audioguru

    TDA7297 cascade channels?

    A long time ago the center tap on a volume control had a series RC to ground and was used for bass boost. If the volume control was set at the center tap or less then the midrange and high frequencies were reduced by the RC and bass went through without reduction. As the volume was turned up...
  13. Audioguru

    TDA7297 cascade channels?

    Since he tried this amplifier to replace the output stage of an old car radio then maybe he overloaded it with a 4 ohm speaker or connected it completely wrong with one speaker wire grounded. Frankchie, 1) Did you select the car radio signal from its volume control? 2) Was the speaker the...
  14. Audioguru

    TDA7297 cascade channels?

    The left and right amplifiers in the TDA7297 are bridged, so each speaker wire is driven with power with no ground. The outputs have a DC voltage on them which cannot be fed to a grounded speaker. The bridged output power is 15W into an 8 ohm speaker when it is turned up too high producing awful...
  15. Audioguru

    Old Resistors

    I never saw a Leslie speaker or looked it up. Did it rotate to make a wah, wah sound?
  16. Audioguru

    Wireless power transfer

    A radio picks up a tiny amount of the massive transmitted power. But the radio still needs a battery or power supply to operate its circuit.
  17. Audioguru

    Wireless power transfer

    The transmitting coil and the receiving coils must be touching each other or almost touching. Wireless headphones transmit infrared or radio signals not power and get the power for their receiver from a battery.
  18. Audioguru

    Old Resistors

    Hevans beat me because I was changing the batteries on a Sudoku thingy.
  19. Audioguru

    Old Resistors

    You do not know the color code so here it is. The resistors are red=2, violet=7, gold= 0.1 times and silver= 10%. So they are 2.7 ohms, 10%. Are you going to guess their power rating?
  20. Audioguru

    Hello can somebody tell me, how come 10mA this current source

    The base-emitter voltage of the 2N5401 Q6 is about 0.62V when it begins to turn on. When Q6 turns on it begins to cutoff Q7 so the current in R9 and Q7 is constant at 0.62V/62 ohms= 10mA.
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