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  1. audioguru2

    frequency to voltage converter

    Hi Alun, I didn't link to the article 'cause it talks more about our vision and CRT's and not much about modulation nor how TV's actually work. I wanted to link to the application note from National Semi in their Analog Handbook called "A color TV primer for engineers" but couldn't find it on...
  2. audioguru2

    frequency to voltage converter

    OOps, I forgot. :-[ The colour quadrature phase modulated carrier is suppressed, and a 9-cycle burst of its carrier is added to the back porch of the horizontal sync pulse to sync the colour TV's colour demodulator. ;D
  3. audioguru2

    frequency to voltage converter

    Hi DR, TV in North America has its luminance (brightness) single-sidband amplitude-modulated with a small vestigial sideband. Its colour is red and blue quadrature phase-modulated 3.79159Mhz higher and the sound is frequency-modulated 4.5MHz higher. The picture is vertically interlaced and each...
  4. audioguru2

    Power Amp

    Hi Kevin, A single simple power transistor used as an amplifier driving a low impedance load is lousy. Modern opamps can deliver at least 24Vp-p into a 10k load with non-linearity so low that you can't hear or see it and can hardly measure it. When you include power emitter-followers in the...
  5. audioguru2

    EPROM Eraser using UV Leds... possible?

    Hi Mauricio, An UV LED is so dim that you need many of them focussed onto the EPROM, or a very long time (years?) to erase an EPROM. A little CR2032 lithium battery can supply up to only about 3mA for a few hours. You might need 300mA or more for a few hours. Try a single UV LED operating at...
  6. audioguru2

    Power Amp

    A power amplifier with toobs! He, he. ;D ;D Kevin, What are you talking about? Power amplifiers must provide a fairly high voltage swing with a fairly high current. Just use a low-current transistor or a few (or an opamp) for the voltage gain and a pair of complementary power transistors as...
  7. audioguru2

    frequency to voltage converter

  8. audioguru2

    Power Amp

    Hi Ruden, Welcome to our forum. ;D There are some power amps in out Projects section. Click the "Projects" button at the top of this page then select "Audio".
  9. audioguru2

    laser lights

    Hi Glen, A 5V regulator like a 7805T would have 19V across it and 65mA through it. Therefore it must dissipate 1.2W and would be very hot without a small heatsink. ;D
  10. audioguru2

    beep or chirp sound

    A piezo transducer is a piezo buzzer without its built-in oscillator. If you drive it with musical frequencies it will play a high-pitched song. You can adjust its volume in steps if you feed it with resistors from multiple outputs from the PIC. You can make it much louder if you drive it with...
  11. audioguru2

    LED FLASHER

    A supply voltage more than about 8.5V might mess-up the timing of the multivibrator if the LEDs are only 1.8V, because the capacitors drive the bases negative to a voltage exceeding the absolute max of 6V rating of the transistor, when the reverse-biased base-emitter will have avalanche...
  12. audioguru2

    Impedance matching.

    A 1000:1 impedance ratio of a transformer designed for a lower impedance would reflect the 8 ohms of the speaker as 8000 ohms to the tubes at low frequencies very well, but would probably be a poor match at high frequencies because it is not designed for the low capacitance which is needed at...
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    OK. The max temp for the inside of the transistor is 200 degrees C. The heatsink can't cool its inside, only its outside (its case). The thermal resistance from the inside to the outside is 1.52 degrees C/W, so if you could keep its case at 25 degrees C somehow, its inside temp with 115W...
  14. audioguru2

    Audio Transformer

    Hi Ante, I've seen some fairly small high power audio transformers that overload an amp below 100Hz. For the same power at 20Hz the transformer is huge. ;D
  15. audioguru2

    help needed hooking up 4 lm3914

    Hi David, The LM3914 is designed to have the brightness of its LEDs controlled by the current from pin 7. Four LM3914's can have their brightness controlled by a single pot that adjusts the current of four current sinks, as attatched. A single 7805 regulator can supply at least 1A if it has an...
  16. audioguru2

    Digital mishaps

    Hi Kevin, I worked with large telephone systems that had many distributed microcontrollers. Interrupts were occuring all over the place and the main microprocessor continued functioning quickly in an orderly fashion. If a complicated circuit has a single microcontroller or microprocessor doing...
  17. audioguru2

    Audio Transformer

    Hi Guys, The physical size of a transformer reveals the lowest frequency it can pass power without saturation. When the core saturates at a low frequency, the primary is just a low resistance piece of wire. ;D
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Maksar, He, he. The way you show cutouts in the heatsink to fit the shoulder of the transistor, you would need to cut the heatsink down the middle for them to be assembled. He, he. ;D ;D Let's calculate the temp of a transistor's chip on that heatsink: 1) The heatsink is 0.33 degrees C/W...
  19. audioguru2

    frequency to voltage converter

    That's correct. AGC is a DC voltage, not a frequency. But it is more complicated because there is one AGC voltage for a TV's IF amplifier that stops at a certain high level, then a 2nd AGC voltage takes over to feed the tuner for higher levels. The AGC voltages might have opposite polarities and...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tedy, A TIP41A would be fine. Most would have less gain than most TIP31A's but their minimum gains are about the same at the fairly low current for it in this project. An "ordinary" TIP31 or TIP41 is rated at only 40V, while the "A" is rated at 60V. With the project powering a low voltage...
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