Recent content by mastrila

  1. mastrila

    Mini Metronome

    Thank you for the advice. I will let you know how things work out. Mastrila
  2. mastrila

    Mini Metronome

    I would like to build the "Mini Metronome" for my daughter. Sure I could buy one but what's the fun (Besides, I do like to impress my kids). The instructions specify that SW1 needs to be "ganged" with P1. Can somebody please explain what this means and how to do it? I plan to replace Q3 (hard...
  3. mastrila

    Replacement for 3DD15A

    I need to replace a 3DD15A power transistor in my power supply. I have not been able to find one where I live. I think that a 2N3055 might work but I am not sure because, whereas I can understand voltage/current/power limits, when it comes to beta, hfe, and the likes I am completely lost. Can...
  4. mastrila

    0-50V 2A Bench Power Supply.

    Ante, thanks again for your advise. What do you mean by "calibration". I will need some (a lot of, in fact) guidance on how to do it. Once that is done (hopefully without blowing anything up), can I measure R off the pot and replace it with a fixed resistor? Can P2 be a 10-20 turn pot...
  5. mastrila

    0-50V 2A Bench Power Supply.

    Ante, thank you for the helpful advise. Yes, I do mean micfoF. I have read your note of caution with interest. I will give it a try anyway since I already have the most expensive component (viz. the transformer) and most of the others. If things do not work out, i can always revert to...
  6. mastrila

    0-50V 2A Bench Power Supply.

    Ante, yes you can. MAXIM has recently posted a modified circuit that allows use of a higher voltage. Anyway, that is not my question. Mastrila.
  7. mastrila

    0-50V 2A Bench Power Supply.

    Hey everyboby, I have a 36V 6A transformer that could be used to built this power supply. Although it likely will not support a full 50V output, it will greatly expand the range of my battery chargers (based on the MAX 712/713). A few questions: 1) The article...
  8. mastrila

    need datasheet for D711

    Hi Ante, thanks again. Do you know what type of transistor it is and a suitable substitute? Mastrila.
  9. mastrila

    need datasheet for D711

    I need to replace a power transistor in switching power supply. The only markings on the metal case (TO-3) are "D711". Could it be a 2SD711? Can you help me find a datasheet for it? Mastrila.
  10. mastrila

    Convert 0-30V 3A PSU to 5A or more

    Hi Ante, thank you for the response. I certainly do not expect to be able to have 3.5A with a 75R load. But I cannot understand why I should not be able to obtain at least 2A (@30V) with 15R, or 1.5A with 20R. Ohm's law is linear. This is my problem. Mastrila.
  11. mastrila

    Convert 0-30V 3A PSU to 5A or more

    I have isolated the VARIAC from the PSU with an isolation transformer (it has taken sometime to find a suitable one) but this has had no effect on my problem with the output. Any fresh idea? Mastrila
  12. mastrila

    0-30 Vdc Stabilized Power Supply

    I have isolated the Variac from the PSU with an isolation transformer but this has not solved the problem with the output. Any fresh idea? Mastrila.
  13. mastrila

    Convert 0-30V 3A PSU to 5A or more

    Ante, thank you for your interest in my problem. The VARIAC is connected to the PSU just like a regular transformer: (AC-Line------>VARIAC------>PSU). I do not understand what you mean by a "full tansformer model". Mastrila.
  14. mastrila

    Convert 0-30V 3A PSU to 5A or more

    I have built this PSU. It looks nice but I am disappointed with its (or my) performance. The maximum current (Imax) and voltage (Vmax) outputs vary widely and proportionally to the resistance of the load (Rload). For example: Rload (Ohms) Imax (Amps) 4...
  15. mastrila

    0-30 Vdc Stabilized Power Supply

    I had an earlier problem with some componemts getting very hot which I eventually traced to a broken trace (pun not intended). Everything is "cool" now but I have another problem that I cannot figure out. I(max) varies with the load. For example, the supply will crank out more than 3.5A with a...
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