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  1. audioguru2

    0-30V Stabilized Power Supply

    It uses an expensive custom-made transformer.
  2. audioguru2

    0-30V Stabilized Power Supply

    Six TIP35 output transistors on a HUGE heatsink and fan will be able to have a maximum continuous output current of 9A or 10A. Then the BD139 driver transistor Q2 will melt. If you use two or three BD139 driver transistors in parallel then opamp U2 that drives them will melt. It is difficult to...
  3. audioguru2

    0-30V Stabilized Power Supply

    The project you copied is not reliable, does not produce 30V at 3A and has many parts overloaded. I fixed it and the new schematic and parts list are in these threads. The fixed version uses a newer real power transistor for the driver Q2 and two output transistors (each with an emitter...
  4. audioguru2

    0-30V Stabilized Power Supply

    Most people's problems with this project are ICs or transistors with their pins connected backwards. Double check the pins with the pictures in the datasheets. If your 2N3055 transistors have not been over-heated and are not fakes then they should work fine.
  5. audioguru2

    Connecting a speaker circuit to a rechargeable battery pack

    A rechargeable 9V little Ni-MH battery can power an amplifier for a short duration. A battery charger IC can be used to make a charger for it. The IC limits the current then shuts off when it detects a full charge. I have a VU meter that has a Ni-MH 9V battery in it for portable use. It is...
  6. audioguru2

    Is this the "ideal" NiCad charger, or is it crude?

    Eveready charged their Ni-Cad battery at 1/20C for 2 Years and the battery performed almost like new. I worked with a wireless tele- conference microphone that used AA Ni-Cad cells. ALL of them ended up shorted after a few years after being continuously trickle-charged. ALL the Ni-Cad cells I...
  7. audioguru2

    0-30V Stabilized Power Supply

    Its voltage might be too low and cause ripple when the project output is 30V/3A. The transformer will not get too hot. Try it.
  8. audioguru2

    0-30V Stabilized Power Supply

    The parts on your perforated circuit board are too far apart. Then the wiring resistance will be too high and the stray capacitance between wires will be too high. Then the circuit will probably oscillate at a high frequency and work very poorly. We recommend using a pcb with a compact layout...
  9. audioguru2

    0-30V Stabilized Power Supply

    When metal parts are connected to 0V then they provide shielding from interference to the circuit. The maximum load for the project is 3A. Then each 0.33 ohm resistor has 1.5A (plus some small base current). The power in each resistor is (1.5A squared) x 0.33 ohms= 0.74W so an ordinary 2W...
  10. audioguru2

    0-30V Stabilized Power Supply

    I started modifying this project. My latest schematic and parts list do not have D10 that I deleted from the original defective version. I added C10 to filter the supply for U3 when I added the 10V zener diode. It is shown on my latest schematic but it is not called D10 and is not called...
  11. audioguru2

    0-30V Stabilized Power Supply

    12000uF is a common value in The West. Use 10000uF or 15000uF instead. Use a 10000uF parallel with a 1000uF, 2200uF, 3300uF or 4700uF. Most of us do not buy electronic parts in a "market", instead we go to an electronics parts distributor store or buy them online where they have millions of...
  12. audioguru2

    can anyone help me connect this circuit

    Many years ago I found the Ultrasonic Radar (motion detector) project but today I couldn't find it. Please provide a link to it. A BC547 is the same as a BC548 except its maximum allowed voltage is 45V instead of 30V. Either transistor can be used in this low voltage circuit.
  13. audioguru2

    CAN SOMEONE TELL ME WHAT KIND OF RELAY SHOULD I USE!!!!!!

    The instructions for the kit say, "we recommend using a 7 to 9 volt relay with a coil resistance of 500 ohms or greater".
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Many of the parts in the original project got too hot and/or were over-voltaged. Then it was not reliable. It could not produce 30VDC at 3A,  instead it produced about 25VDC at 3A with lots of ripple. Maybe somebody used this project to charge a battery and the diode prevents the battery from...
  15. audioguru2

    0-30V Stabilized Power Supply

    With a 30VAC transformer, the positive supply is 42.4VDC. If the output is shorted or is at a low voltage and the current is set to 5A then the output transistors dissipate 42.4V x 5A= 212W! 70.7W each is too much. Three 2N3055 transistors can do it if they are cooled so that their case is at 25...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    I don't think anybody said that before. How can it be destroyed when it is switched off? The modified schematic has been posted on this website a few hundred times. It uses a transformer with a high enough voltage so the circuit can produce 30VDC at 3A. The original circuit could not. Its new...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    But the maximum supply voltage (only 36V) for the LF411 (and for the TL081) is too low for this project. Using an LF411A with a maximum supply voltage of 44V will be better.
  18. audioguru2

    New electronics hobbyist looking for good projects to start on!

    RadioShack is gone from Canada because they sold cheap Chinese parts (audio cables for example) at 10 times the price for exactly the same junk as sold at The Dollar Store. I returned to RadioShack the cable I bought at The Dollar Store and got my ripped off money back. Some RadioShack stores...
  19. audioguru2

    Capacitors

    Yes, there are a lot of flashing ads here. There is also a lot of SPAM until a moderator comes and cleans them out. Many nOObs come here to say things that are wrong. Many projects here did not work until I fixed them. I have not been here for a long time so there are probably many new...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    If the case is connected to the wall plug ground then the negative supply of this project or its 0V output will be around -40VDC if the positive rail is shorted to the case. Probably bad insulation from the driver or output transistor case to its heatsink which is probably bolted to the case.
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