Recent content by WHONOES

  1. WHONOES

    Tantalum capacitors Vs. Aluminium capacitors for synchronous switching converter input pin.

    I generally use Aluminium.
  2. WHONOES

    Tantalum capacitors Vs. Aluminium capacitors for synchronous switching converter input pin.

    Input capacitors for voltage regulators are there to decouple the device from the inductance of the wiring or pcb track supplying it and should be placed as close as physically possible (immediately adjacent is best). Failing to do so may cause the regulator to oscillate. Note that an output...
  3. WHONOES

    Amplifier biased too hot?

    Further to my comments on using "Pots" in VBE multiplier circuits. The wipers on multiturn potentiometers can be sensitive to vibration particularly post adjustment. Therefore, after making an adjustment and whilst still monitoring current flow, tap the "Pot" with a small screwdriver or...
  4. WHONOES

    Amplifier biased too hot?

    I prefer the term "VBE Multiplier" because that is exactly what it is.
  5. WHONOES

    Buck converter calculation does not match with LTspice results

    You may need to add a small amount of resistance in series with you inductor otherwise the simulator will regard it as a perfect inductor with an infinite Q with attendant simulation issues. 100 milli Ohm would be a good place to start.
  6. WHONOES

    Buck converter calculation does not match with LTspice results

    A useful document that I have used in the past is "Buck-Converter Design Demystified" written by Donald Schelle and Jorge Castorena of Maxi Integrated Products. You should be able to find it via "ElectronicDesign" web site using the below link...
  7. WHONOES

    How to increase high voltage from ignition coil using diode + inductor?

    The normal way to increase the O/P of an ignition coil is to increase the voltage applied to the "Primary" side of the coil. This is usually achieved with a circuit that charges up a capacitor to a couple of hundred volts or more and then discharge it into the "Primary" via a thyristor.
  8. WHONOES

    Amplifier biased too hot?

    There is certainly an argument for leaving a Pot in circuit as it allows easy adjustment. In BJT amplifiers that use the VBE multiplier biasing arrangement, the Pot should be across the Base Emitter junction of the transistor. Then if it goes open circuit, the VBE multiplier transistor gets...
  9. WHONOES

    Amplifier biased too hot?

    Hi Tom. I'm pleased that it worked out for you and your amplifier. The procedure is fairly straight forward but, if you are not familiar with class AB output stages and how they are biased, they can be a bit of a head scratcher. Regards Whonoes
  10. WHONOES

    Amplifier biased too hot?

    Have had a look at the supplied schematic. To adjust the output idle current, use the following procedure. Referring to the amplifier circuit at the top of the schematic. 1) Make sure that the input to the power amplifier is shorted. The easiest way to do this in to use a phono plug containing...
  11. WHONOES

    E-mu 1820M - outputs low and distorted after some work on it

    Have you created a solder zit between two pads by any chance?
  12. WHONOES

    JBL Bar 2.1 Mk2 making screeching sound when audio is played.

    Some Switch Mode Power Supplies tend to go into "Intermittent mode" when lightly loaded. This tends to make the transformer squeak. A fault in the SMPS feedback loop may cause a similar fault. Either way, a substantial ac ripple will likely be present on the SMPS output. If it is the latter...
  13. WHONOES

    Question regarding creating a boost circuit, 24 to 200V for a solenoid

    Can you please describe exactly what you are trying to do with your circuit. A proper circuit description detailing the contribution of each component would be a bonus. Is your device intended to run continuously or only upon a prompt from its user? What is the purpose of the inductor in the...
  14. WHONOES

    Speaker box project. Need a little help

    I built something very similar a short while ago. If I need it to run for an extended period, I just leave the charger plugged in and charging and use it like that. No complicated switching needed then!!
  15. WHONOES

    Need a little help understanding the way my class AB power amplifier works.

    Additions to the circuit description already supplied. R2 and R3 connected to the emitters of the Tp1 and Tp2 forming the current mirror will provide a small amount of negative feedback. This will help to linearize the amplifiers response thus reducing distortion. R4 and R5 perform a similar...
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