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  1. audioguru2

    i need some lm358, could you give me some advice for it?

    The LM358 is an old low power dual opamp that produces poor quality signals. Are you a Spammer who is selling Chinese copies at HQEW?
  2. audioguru2

    0-30V Stabilized Power Supply

    The first page of the datasheet from Analog Devices spec's a max supply of only 36V but later it says 44V so it is very confusing. I would not use more than 36V. It is wrong to overload parts. The original circuit cannot produce a regulated (no hum) +30.0V at 3.0A. C4 and C5 are simple filters...
  3. audioguru2

    0-30V Stabilized Power Supply

    You didn't buy a transformer that has a 24V AC or 28V AC output. Instead you bought a switched mode power supply with a choice of DC outputs which is no good for this project. The modified project has a 28V AC or 30V AC transformer that is rectified and filtered and it produces +40.2V DC and...
  4. audioguru2

    0-30V Stabilized Power Supply

    The OP07 opamps will be destroyed in the original circuit because their maximum supply is plus and minus 18V (a total of 36V) but the 24V AC transformer will be 26V AC with no load and the positive unregulated supply will be +35.4V DC. U2 and U3 also have the -5.6V supply so their maximum supply...
  5. audioguru2

    Checking Mosfets

    Your multimeter turned on the Mosfet and charged the gate-source capacitance that kept it turned on. The gate-source has an extremely low leakage current so the gate charge might last for a fairly long time.
  6. audioguru2

    Pirated content

    Lots of sites copy circuits from other sites. But it doesn't matter because most of the circuits do not work.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    No. When a 28V AC or 30V AC 120VA transformer is used then the output at 30.0V and 3A will be regulated perfectly with no hum. There is hum when the transformer voltage is too low which causes the output transistors, driver transistor and opamp U2 to be saturated.
  8. audioguru2

    Getting stable volume(sound) level even when I/P sound level is increased/decrea

    Look in Google for an audio compressor limiter circuit. When the average input becomes too high then it reduces the level down to normal. When the average level becomes too low then it increases it up to normal but it also increases background noise when there is no program sound. Some audio...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    When the output of a "regulated" power supply has hum (100Hz in Europe or 120Hz in North America) then it indicates that the output is saturated and is not regulating the voltage. The voltage changes of the AC input (including noise) and the ripple of the filtered rectifier are simply passed to...
  10. audioguru2

    0-30V Stabilized Power Supply

    Nobody knows if the circuit will work with your tiny transformers. If it does not work then you will not know if something in the circuit is wrong so the test will be useless. Your tiny transformers might produce 46V AC without a load then the unregulated supply to the circuit will be 64V DC and...
  11. audioguru2

    0-30V Stabilized Power Supply

    1) The voltage and current from the transformers are much too small. 2) The circuit needs two 2N3055 output transistors not just one. 3) Each output transistor needs a 0.33 ohm emitter resistor, not a 33 ohm resistor.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Your transformer has an output voltage too low so I don't know if the maximum output voltage from the project at a current of 3A is 24V DC or 25V DC. It might have excellent voltage regulation at 24V DC but produce a lot of hum riding on 25V DC.
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Didn't you see the latest parts list? To have a 30V DC output then the transformer must be 28V AC or 30V AC. Since your transformer is only 24V AC then the max output will be only 24V DC or 25V DC. The transformer must have a currenty rating of 4.2A AC for the output of the project to be 3A...
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    If you use a 28VAC or 30VAC transformer at 4.2A then the max output should be higher than 30VDC at 3.5A and the calibration trimpots should reduce the max output to 30VDC at 3.0A.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    The unregulated positive voltage is  higher than 42V (when there is no load) which is very close to the max allowed voltage of 45V for a BD135. A BD139 is rated at 100V. A transistor is measured like two diodes. The base-emitter is one diode and the base-collector is the other diode. When a...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    Your mistake might have damaged the BD139 driver transistor or the 2N3055 output transistors.
  17. audioguru2

    0-30V Stabilized Power Supply

    Sorry but I don't have time to look at the datasheets of your Oriental transistors. The spec's for a 2N3055 transistor are a Vceo of 60V, a minimum hFE of 20 at 4A and a max power dissipation of 115W. If your transistors are the same or better then they can be used.
  18. audioguru2

    Sound Level Indicator

    Yes you can use two MC33171 instead of one MC33172. Both must be powered.
  19. audioguru2

    Sound Level Indicator

    Go to www.farnell.com and look to see if they have an office in your country and have the IC. The MC33172 works well up to 35kHz. You can use an LM358 (its pin numbers are the same) but it has poor performance above 2kHz. You can use an MC34072 (it also has the same pin numbers) but its supply...
  20. audioguru2

    0-30V Stabilized Power Supply

    Whose schematic are you looking at? My schematic is correct. U1 does not have its pins flipped. U1 is the 11.2V reference voltage circuit.
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