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  1. Audioguru

    Bench power supply upgrade

    Maybe your supply voltage is 12V then the series resistor has (12V - 5.1V=) 6.9V across it. The circuit needs 6mA and maybe the datasheet for the zener diode says it needs 20mA. Then the total current in the resistor is 26mA and Ohm's Law calculates the resistor to be 6.9V/26mA= 265 ohms but use...
  2. Audioguru

    Bench power supply upgrade

    If you feed a higher voltage to a zener diode then it burns out. Instead you limit the zener diode current with a series resistor. The datasheet of the zener diode part number shows its recommended current.
  3. Audioguru

    Bench power supply upgrade

    The Chinese circuit uses a 5.1V zener diode to regulate the 5.1V. A 5V phone "charger" does not use a voltage regulator so the 5V will change often and might even be pulsing. The 5.1V current is only 6mA.
  4. Audioguru

    Help with work to finish my college. Help me please!

    I wonder if Circuit Digest in India also copied the circuit?
  5. Audioguru

    Will this power a bench supply kit?

    There are many fake products and fake reviews "over there". Without a load, most 24VAC transformers produce 25VAC or more. Rectified it produces 34VDC. It also has a negative 5.1V for the opamps then they get 34V + 5.1V= 39.1V or more but their absolute maximum allowed supply is only 36V. The...
  6. Audioguru

    Will this power a bench supply kit?

    When you buy cheap junk from "over there" then you get cheap junk. That power supply is a Chinese copy of an old kit from Europe that powers its old opamps with a voltage higher than their max allowed voltage, has many parts overloaded and they get way too hot. It does not produce regulated 30V...
  7. Audioguru

    Strange battery behaviour in portable radio?

    if the DAB radio draws its rated 500mA from a 6V battery then it heats with 3W and it would probably burn your hand if you held it.
  8. Audioguru

    Connecting multiple piezo ceramic elements in a sound installation

    A resistor parallel with each piezo simply loads down the amplifier more causing the amplifier to be overloaded. A resistor in series with each piezo reduces the effect of its high capacitance overloading the amplifier but causes high audio frequencies to be reduced so there is almost no sound.
  9. Audioguru

    Connecting multiple piezo ceramic elements in a sound installation

    Why play the sounds of insects and ticking? I also heard a few short duration high frequency beeps in the video. Try any amplifier and if it blows up then try another then another until you find an amplifier that survives.
  10. Audioguru

    Strange battery behaviour in portable radio?

    Energizer AA Ni-MH batteries are 2300mAh and are made in Japan. Good quality. Some Duracell AA Ni-MH batteries are 1300mAh and are made in China. Poor quality.
  11. Audioguru

    Strange battery behaviour in portable radio?

    Maybe the digital circuit uses very old power-hungry TTL logic ICs.
  12. Audioguru

    Strange battery behaviour in portable radio?

    Uniross sells cheap 1000, up to good 2700 AA rechargeable batteries. The number might be mAh. The specs for the digital radio says it draws 500mA which is 2.5W. An ordinary radio draws much less current.
  13. Audioguru

    Connecting multiple piezo ceramic elements in a sound installation

    The specs for the piezos shows that they have a high capacitance that cuts high frequencies when fed from a series resistor and the capacitance is multiplied by your quantity of 100 for one piezo and another 100 for the other piezo.. An audio amplifier can be destroyed when driving such a high...
  14. Audioguru

    Connecting multiple piezo ceramic elements in a sound installation

    What kind of sounds will your many piezos play? The cheap piezo elements are designed to be the single sound frequency beeper in a smoke alarm. They are not to be fed from an audio amplifier because they are useless for music and will cause a voice to be very tiny and beepy. None of the Chinese...
  15. Audioguru

    Good source for Weller WTCP tips?

    I have always used PTA7 tips with 63/37 leaded rosin-core solder.
  16. Audioguru

    Battery Questions??

    The cheap no-name-brand ebay charger module is made to charge a much larger 18650 cell phone battery at 1A. Little Li-Po batteries charge at much less current to avoid an explosion and fire.
  17. Audioguru

    Good source for Weller WTCP tips?

    I have a Weller WTCP soldering iron that is about 55 years old. Usually its tip lasts for about 5 years but the last tip I bought from a local store (the store name and staff are from a distant country) looked like a Weller but it fell apart in a couple of months. There are fakes everywhere but...
  18. Audioguru

    Good source for Weller WTCP tips?

    Amazon sells clothes and shoes. They know nothing about electronics but they sell cheap soldering iron tips for a Weller soldering irons but not made by Weller, they are made by Teche. I looked in Google for Teche Company but found nothing. A Chinese knockoff? The tips are not WTCP anyway.
  19. Audioguru

    Battery Questions??

    A Lithium battery is charged with a Lithium battery charger circuit. A power bank uses a 5V USB input for its charger circuit to charge its Lithium battery, not a high voltage.
  20. Audioguru

    Battery Questions??

    The battery you showed is a single cell "Li-PO". Most do not have a charger circuit inside them but some have a protection circuit to prevent a disaster. The cell is 4.20V fully charged and a higher voltage will probably cause an explosion and fire if there is no protection circuit inside the...
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