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  1. Audioguru

    LM339/LM339N can't get output high

    That is why I and everybody else said it needs an output pullup resistor added. An LM339 has 4 comparators. An LM393 has only 2 of the same comparators.
  2. Audioguru

    LM339/LM339N can't get output high

    Sorry to say you are wrong, you say the logic backwards that is very confusing to new people. The datasheet shows that it is the same as an opamp that has an output pullup resistor: When the + input has a higher voltage than the - input then the output goes high. It inverts and the output goes...
  3. Audioguru

    Why is it PNP instead of PPN for transistors

    Tiny little surface-mount parts are mounted and soldered with a machine. I am not a machine so I use through-hole parts.
  4. Audioguru

    Why is it PNP instead of PPN for transistors

    If you buy transistors from a real local electronic parts distributor and not fake ones from ebay then the distributor or Google has the manufacurer's datasheet that shows which pin is which. That is why I buy parts from Digikey and look on Google. I design and plan a parts layout for a circuit...
  5. Audioguru

    QSC Power Amp gets hot

    Your numbers 1.18 and 2.77 cannot be the supply voltage of the stereo amplifiers that produce 50W into 8 ohms. Their supply will be at least 60V or more than plus 30V and minus 30V.
  6. Audioguru

    Why is it PNP instead of PPN for transistors

    Simply look at the datasheet of a transistor. For example, the 2N3906. Its maximum allowed reverse-biased emitter base is only 6V but is usually never reverse biased. I have never tried it but when it is connected backwards, its current gain is only about 7 times instead if its normal 200 times.
  7. Audioguru

    LM339/LM339N can't get output high

    The photo of wires all over the place in a breadboard is not a schematic. The datasheet of the LM339 and LM393 comparators show that the outputs ore NPN transistors with open connectors for you to attach together and/or with a load to the positive supply. You should always look at the datasheet.
  8. Audioguru

    multivibrator circuit

    You did not say the high frequency number. The Mosfets you want to drive have a high gate-source input capacitance that takes a fairly high current for the Mosfets to work at a high frequency. The CD4047 output current is not high enough, buffers are needed to boost the output currents of the...
  9. Audioguru

    multivibrator circuit

    You can make a simple 2-transistors multivibrator oscillator or use an oscillator IC like this one:
  10. Audioguru

    multivibrator circuit

    I agree that the extremely simple circuit has no control of starting, the frequency or the voltage and is not used in products. Oh, maybe it is used in a mosquito zapper.
  11. Audioguru

    Newbie Questions - sequential led lights

    A flat battery is a dead one or a Li-PO one. My radio controlled model airplanes use two-cell 7.4V to 8.4V Li-PO rechargeable batteries. Very small model airplanes and small drones use a very small and flat single cell 3.7V to 4.2V Li-PO battery that cannot light a modern very bright green, blue...
  12. Audioguru

    RGB LEDs

    The math is wrong again. (14V - 2.1V)/820 ohms= 14.5mA, or 14.5 thousand micro-amps. Maybe he used 820k ohms for 14.5uA?
  13. Audioguru

    Newbie Questions - sequential led lights

    Are the green lights LEDs or old fashioned light bulbs? A 4017 has 10 outputs for LEDs but a second one can be added for more outputs. Will you power the lights with a battery or with an AC-DC power supply?
  14. Audioguru

    Newbie Questions - sequential led lights

    A CD4017 is a forwards sequencing counter that is made to go back with diodes. It has a fairly low output current needing transistors at each output to boost the currents. I used a 74HC4017 sequencer that has so much output current that it needs current-limiting resistors. I clock it with a Cmos...
  15. Audioguru

    Noob question - clap activated pcb

    If the LEDs do not work for long then maybe you have a cheap low quality battery. There is a huge difference between a good battery from USA or Europe compared with a junky Chinese battery bought at The Dollar Store.
  16. Audioguru

    RGB LEDs

    You made an arithmatic error. If the green LED is a very bright modern 3.4V one then it has the same chemistry as a white and blue LED. If the green LED is a dimmer old one then it is about 2.2V. Why 14V? In a car? (14V - 3.4V)/3M= 3.4uA, not 3.4pA. Maybe your 3M resistor is actually only 30k ohms?
  17. Audioguru

    Understanding of the circuit

    Many power supplies produce hum and hiss noises. The value of C59 is too low to reduce hum but it does reduce power supply hiss.
  18. Audioguru

    I have a 48 volt power supply with 15 amps. OkI only need 6 amps. What size resistor can I use that

    The electrical receptacles in my home provide 120V at up to 15A. But my clock draws a current of only 2mA (0.002A) from the 120V. The clock will NEVER draw the available 15A.
  19. Audioguru

    Replace IC 4049

    The datasheet for the CD4049 shows that with a 12V supply its typical average output sink current is 25mA and its source current is 12mA per inverter. The circuit has 3 times those currents with the 3 inverters in parallel.
  20. Audioguru

    Replace IC 4049

    Why is you sketch showing the CD4027 connected to the Mosfets without the CD4049 or the complementary transistors? It should work like that but the Mosfets will switch slowly and get very hot. Then you said the CD4049 has a 5V swing which is way too low! Then you said the transistor emitters...
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