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  1. audioguru2

    0-30V Stabilized Power Supply

    Hi Lighty, I notice that 2N3055 transistors have collector to emitter leakage current of 0.7mA max so two have 1.4mA. Then when there is no output load current the output voltage rises. Try two new 2N3055 transistors to see if they are much better. Also replace D11 that might be leaking current...
  2. audioguru2

    0-30V Stabilized Power Supply

    There is your problem. The output of U2 is the base voltage of Q2 which is only 0.08V. The emitter is much less because Q2 is an emitter-follower so should be at 0V (measure it and report here). Q4 and Q5 are also emitter-followers with a base voltage of 0V so their emitters at the output should...
  3. audioguru2

    0-30V Stabilized Power Supply

    Hi Lighty, The current regulator is supposed to reduce the output voltage when the output is shorted. But since your output voltage is never less than 0.7V then the shorted current is too high. The TLE2141 opamp has inputs that work at 0V and has an output that goes almost to 0V. When the...
  4. audioguru2

    Give me some help pls..

    You have a lecturer and a teacher. They have failed their jobs because they didn't teach you how to design your power supply assignment. Teachers and lecturers in most countries actually teach electronics to students so the assignments are done correctly, not just copied from somebody else. It...
  5. audioguru2

    Sony Trinitron KV-XA21N93 - Scanning lines problem

    A TV is supposed to have scanning lines. They draw the picture. Maybe you mean that the retrace lines are visible. The retrace occurs when the beam is supposed to be turned off so it can return to the left side or to the top where it can be turned on to make the next scanning line.
  6. audioguru2

    0-30V Stabilized Power Supply

    With the output current set to 6A and the output is shorted then the output transistors must dissipate a total of 39V x 6A= 234W of heat. You can use two powerful transistors with a fan or use hundreds of little transistors each with a little heatsink. The amount of heat dissipated is the same.
  7. audioguru2

    c828 transistor

    Hi Eplanet, Your "equalizer" circuit is probably just a bass, midrange and treble tone controls circuit with a gain of only 1. It can cut its frequency bands, boost them or leave them flat. It feeds a power amplifier that feeds a speaker.
  8. audioguru2

    0-30V Stabilized Power Supply

    A darlington transistor or two fast transistors connected as a darlington are too slow. Why do you want four 2N3055 output transistors? To have a max output current of 6A? Then each has a max current of 1.5A when the minimum current gain of a 2N3055 transistor is about 41 then the max current...
  9. audioguru2

    c828 transistor

    It is probably an Oriental 2SC828 transistor. Go to www.datasheetarchive.com to see its spec's and to see substitution guides.
  10. audioguru2

    0-30V Stabilized Power Supply

    The BD139 is a very fast transistor which is why it was selected. The TIP112 is far too slow and will cause the output amplifier to oscillator or have very poor transient response. Years ago I replaced the little 2N2219 with a TIP31 transistor and another member showed that its slow speed...
  11. audioguru2

    Help required for transmitter / receiver

    The circuits are extremely simple and have poor performance. They were used in child's toy cars about 15 years ago and cost almost nothing at $10.00. Maybe they are still available.
  12. audioguru2

    0-30V Stabilized Power Supply

    Your voltmeter does not measure correctly.
  13. audioguru2

    0-30V Stabilized Power Supply

    Measure the voltage with a portable voltmeter (not connected to earth).
  14. audioguru2

    Lithium-ion battery Cycle

    Go to http://batteryuniversity.com/ to learn about batteries. A rechargeable Lithium cell is 4.2V when fully charged. Its voltage quickly drops to 3.7V when it is used then drops slowly to 3.0V. Its load must be disconnected when its voltage reaches 3.0V or it is damaged. It must not be...
  15. audioguru2

    FM Transmitter Help

    Measure the battery voltage and measure how much current the transmitter is using. My transmitter used a brand new 9V alkaline battery that measured 9.2V when new and 8.0V after one hour. The current was 53ma when the battery was new. I measured the range across a huge river valley with nothing...
  16. audioguru2

    0-30V Stabilized Power Supply

    I do not see how you can measure a voltage as high as +54VDC.
  17. audioguru2

    0-30V Stabilized Power Supply

    Hi Ultima, The input bias current of a TLE2141 opamp is 2uA max. Then its current in R21 (10k ohms) causes an input offset voltage of 20mV at U3. R17 is only 33 ohms which produces a voltage of only 4mV so increase its value to up to 200 ohms to fix your problem.
  18. audioguru2

    SC480 power amp full

    Of course it was a good project at Silicon Chip magazine about 7 years ago. It is still a good amplifier project.
  19. audioguru2

    0-30V Stabilized Power Supply

    Maybe you are talking about the 0.47 ohm/10W resistor R7 that senses how much output current? If you change it to only 0.1 ohms then the current regulator parts also must be changed. The input offset voltage of opamp U3 must be nulled to compensate.
  20. audioguru2

    what the hell is this circuit? weird opamps

    The Sallen and Key highpass filter needs to be driven from a very low impedance. The output of the first opamp is a very low impedance. R5 in your sketch appears to be in the wrong location which might explain why TINA doesn't work with it.
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