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  1. audioguru2

    0-30V Stabilized Power Supply

    Replace the tiny 2N2219 driver transistor with a BD139 power transistor on a proper heatsink. For an output of 2.5ADC the 24V transformer must deliver 33.9V at 2.5A which is 84.8VA. Then a 24V/3.5A transformer must be used. The original TL081 opamps have a max allowed total supply voltage of...
  2. audioguru2

    Christmas Light Problem

    I think you should buy a diode from a real electronics parts distributor. Maybe Radio Shack sells defective parts (seconds or sweepings off the floor of the manufacturer). Then the lights will operate at half power. My electrical utility company gives away for free one set of new low power LED...
  3. audioguru2

    Christmas Light Problem

    If the lights are incandescent then connect a diode (1N4007) in series to cut their power in half.
  4. audioguru2

    Plants Watering Watcher-2

    My daughter said that hers stopped working and needs to be fixed. Its LED did not light when it had the high resistance of dry soil or nothing between its probes. Duh! Its 3V battery was only 0.45V. It probably stopped working months ago. A pair of new AAA alkaline cells fixed it.
  5. audioguru2

    Input and Output impedance

    Why not use an opamp? Its output impedance is almost zero.
  6. audioguru2

    Active filters

    An active filter adds some positive feedback at the cutoff frequency so the response is flat to the cutoff then a sharp slope. A multiple-feedback bandpass filter can have any Q you want. A simple highpass filter then a simple highpass filter is a very poor bandpass filter. Both filters...
  7. audioguru2

    circuit distortion

    The TL071 single, TL072 dual and TL074 quad audio opamps are inexpensive and have distortion of only 0.003%. The OPA134 single, OPA2134 dual and OPA4134 quad audio opampscost a little more and have distortion of only 0.00008%. Two or three transistors have much more distortion.
  8. audioguru2

    circuit distortion

    A transistor has a max open loop voltage gain of about 280 and distortion at full output of about 40%. If it has negative feedback to reduce its gain and distortion then its gain is 3 and its distortion is 1%. Two transistors with bootstrapping have distortion of 0.015 at lw levels rising to...
  9. audioguru2

    where is transducer and transmitter in PCB Board in ultrasonic radar project

    It is not ultrasonic radar nor sonar. Instead it is a simple ultrasonic motion detector. The schematic has errors. The receiving transducer is shown connected to terminals 3 and 4. The transmitter transducer is shown connected to termonals 5 and 6.
  10. audioguru2

    Current Regulator Circuit

    Since you already have a negative control voltage then use it to control your negative current source.
  11. audioguru2

    AM Reciever (Reply please! as soon as possible)

    I am sorry to double-post but if you look at the schematic this is not a regenerative circuit. The 120k resistor provides DC negative feedback, not RF positive feedback. The first two transistors simply amplify the signal from the tuned circuit then one transistor clips the signal which...
  12. audioguru2

    AM Reciever (Reply please! as soon as possible)

    The article says that the author used the ferrite bar antenna coil and tuning capacitor from an old AM radio. Most AM radios use a ferrite bar with a coil of wire wrapped around it for a tuned antenna. AM radios about 50 years ago used just a pretty big coil of wire for an antenna. Crystal...
  13. audioguru2

    Current Regulator Circuit

    When you save a schematic as a JPG file type then it is very fuzzy. Save it as a PNG or GIF file type for a schematic to be very clear. The negative current source circuit needs a negative input voltage. Invert the positive input with an inverting opamp then feed the negative input to your...
  14. audioguru2

    There is a trojan pc virus here today.

    Today the trojan virus is gone from the home page. The home page stops loading when it tries to show a picture from www.mypagerank.net . One time today my Internet Explorer 8 jammed and said "Electronics-Lab not responding" so I could not navigate nor log off. No other site I visit does this.
  15. audioguru2

    There is a trojan pc virus here today.

    I receive the virus only on the home page. It does not appear during a reply. Here is the warning:
  16. audioguru2

    There is a trojan pc virus here today.

    Twice today when I logged in here my anti-virus software detected a trojan virus and deleted the file. The third time it couldn't delete the file and recommended a re-boot which deleted the file. Maybe I will not come here anymore to be greeted with pc viruses. Most of the time I cannot...
  17. audioguru2

    There is a trojan pc virus here today.

    I entered this site 3 times today. Each time my anti-virus software reported receiving the same trojan virus that it deleted. For months this site has caused my Internet Explorer to report "Not responding" when I try to navigate and I must "Control Alt Delete" to close it and get away.
  18. audioguru2

    0-30V Stabilized Power Supply

    The National Semi LM355 is obsolete and has not been made for 11 years. Its max allowed supply was only 36V but was 44v for the more expensive LF155. They will not work in the latest circuit because their input common-mode range does not go as low as the MC34071 or the TLE2141. The LF355 is...
  19. audioguru2

    0-30V Stabilized Power Supply

    Nand, are you blind?
  20. audioguru2

    Guitar Aplifier

    You blew up the amplifier with a supply voltage that was double what it was supposed to be. It still has problems. An audio amplifier does not use and does not need an LC filter.
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