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  • #10101

    Jean-Pierre Desrochers
    Forum Participant

    Hi guys,

    Because one of my latest passion is vintage radios repairs
    I started many years ago to look at some repair GURU’s videos on Youtube.
    I discovered that to get efficient at radio repair you need
    to own a minimum of RF and metering test equipment.
    One of these test equipment would also be an isolated variable power supply
    for testing AA5 (All american radio) non isolated radios
    that have live chassis..
    Because most of these Variable AC supplies are expensives
    I decided to build my own with available parts.

    This project of mine is viewable here:
    http://www.arcenson.com/projects/AC_Isolated_Variable_Power_Supply/

    I hope this project could help some people to build their own.

    Enjoy !
    Jean-Pierre

    #10142

    Bruce Winter
    CVRS Member

    Jean-Pierre –
    Thanks for taking the time to put together the DIY variable AC supply. Very well done.
    How linear did the meter readings turn out?
    What schematic design program do you use – the result looks very neat.
    No ground connection on the output receptacles – any reason for that ? For safety, I would have had the ground wired.
    I’ll take a look at frontdesigner3.0 for a project I have in mind – thanks for the reference.
    Regards, Bruce

    #10143

    Jean-Pierre Desrochers
    Forum Participant

    Thanks Bruce for your nice comments..
    — How linear did the meter readings turn out?
    Well I had to do some tests to find the ‘appropriate’ components for each meter..
    the 0-1mA meter (0-130vac modified) was friendly to accomodate because of the large voltage
    I had to reduce to this current range.The voltage drop in the 1N4007 (D2) would not interfere
    in the linearity at all. I would say linearity wise I ended up in the 2-3% precision !!
    The 0-100mA meter (0-4amp modified) was more touchy..The low current transformer output
    needed not to be modified by any non-linear component (like the 1N60 germanium diode D1)
    including the current transformer voltage output non-linearity region (when used with current too high).
    There has been a ‘sweet spot’ just before the transformer curve started to be non-linear.
    I used that max current at 4amp RMS. Again very good linearity around 2-3%.

    — What schematic design program do you use – the result looks very neat.
    I always used OrCAD Capture and Layout CADs since the 90’s.
    Capture produces very ‘elegant’ schematics compared to many others CADs (like Eagle not to name it..)

    — No ground connection on the output receptacles – any reason for that ? For safety, I would have had the ground wired.
    Well I’m still wondering if I would need one.. The radios that will be on test will be with live chassis
    and these chassis will be isolated by this supply and grounded from my tests Equipment probes & leads so.. Hmmm. Don’t know..

    — I’ll take a look at frontdesigner3.0 for a project I have in mind – thanks for the reference.
    This is a MUST HAVE for front panel designs.
    If you have time to take a look at some of my modular synthesizer modules projects
    you will find MANY front panel layouts made out of FrontDesigner3.0 .
    Just to get its meter graticule maker tool this software Worth it !!
    The modular modules build details are here:
    http://www.arcenson.com/projects/Modular/
    By the way, I will have a 4.0A fuse added in series with the variac’s cursor
    as many readers recommended it for safety of the auto-transformer
    specialy at low secondary voltage with too HIGH current..

    Thank you for your time.
    Jean-Pierre Desrochers

    #10146

    Bruce Winter
    CVRS Member

    Jean-Pierre –
    I’m afraid the cost of OrCad ($300.00 for 1 year license) is outside of my budget for just the occasional use. I would not need all the professional features. There are several free open source programs. I am trying one called Fritzing which is quite supportive of the Arduino boards in projects. Somewhat of a learning curve and it tends to use symbolic symbols for the components rather than the traditional old school schematic symbols which I am use to.
    As for grounding the output receptacles, I realize vintage radios had a two wire plug without a ground, but even the Hammond 171 & 172 series isolation transformers have the ground connected.
    The fuse in the output of the variac was a wise move as I have seen too many cooked variac windings that were overloaded.

    Thanks again,
    Bruce

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