bench power supply design help

Discussion in 'The Projects Forum' started by swmitchell, Nov 18, 2014.

  1. swmitchell

    Thread Starter New Member

    Nov 14, 2013
    Hi everyone!

    I've been reading these threads along time and learned a lot from all your help.

    I've been given an old transformer. Its a beast of a thing. But it outputs 75v. I'd lime to make it into my bench power supply.... Perhaps do a rewind on it.

    I've done the regulator / 2n3055 thing already... Could I do the same with a 2n3773. And not re tap it. I could put a few zenner diodes for the base voltage... I'm wondering what you people would do?
    I'm not planing any projects above 50v...
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    You could use that one.
    The problem everyone gets into with supplies starting with such a high voltage is that the power in the transistors goes out of sight at low output voltages.
    After you rectify and filter it the output will be around a 105 volts. So if you want the output of the supply to be 5 volts at 5 amps the power transistors will need to handle 500 watts. :eek:
    Suddenly you have a space heater.
  3. Lestraveled

    Well-Known Member

    May 19, 2014
    First thing......Do you really need a "beast" power supply? Sure, designing it and learning about all the issues effecting a linear power supply will teach you a lot about power and heat dissipation. But.....after buying and assembling the big parts, heat sinks, fans, etc, etc, how often will you need more than 200 ma at 15 volts?
    You will learn a lot from rewinding that transformer to give you two 18 volt windings. I suggest you do it. I and many people here have done it. Here is a picture of the latest transformer I rewound. It is a monster.


    Looks really cool, but.....will I ever use it in a bench power supply?? Nope...... I might use this in an experiment or a special project once every couple years and that is it.

    Want to know what power supple I use the most?? A 1972 dual, 1.5 amp, 0 to 30 volt, power supply made by Harrison Labs. I have a few others but that is the one that stays on the most.

    It is good for you to design something beyond your expectations, but is it wise to spend the effort to build it?? You are the only person that can make that call.

    No matter what you do, have fun.