317 vs 723 regulator question

Discussion in 'Homebrew and Kit Projects' started by WD5ABC, Dec 20, 2008.

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  1. WD5ABC

    WD5ABC Ham Member QRZ Page

    Thanks for the links, I'm looking at them now. I'll be using this supply to run my Yaesu FT-990 or similar load.

    Kerry, WD5ABC
  2. PA5COR

    PA5COR Ham Member QRZ Page

    No problem, if you need more info, just let me know

    Have fun building the regulator unit.

  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    That is an elegant regular design simpler then a 723, and seems to do everything the 723 does.

    There are a lot of OEM PSU's that use the 723 design they can be had surpuls for pennies on the dollar I still have a few in my roommate's garage. Those regular boards can be easily modified for high cutrrent use. That makes them real attractive for ham power supplies. The only issue that has been largely overlooked in this discussion is overvoltage protection. A few bucks worth of parts can make the difference between reparing a power supply and repairing both a transciever and a power supply. I have seen Astron power supplies fail and go to the top rail, that is going to hurt a transciever that happens to be turned on at the time and a few regardless of being on or not.

    My current power supply is a Powertech OEM that was built in the late 70's. The supply uses a 723 and has over voltage protection. This box probibly has 50,000+ hours on it. The only thing I have ever done is blow the dust out of it and test the OVP once and a while. One of these days I am going to rebuild it maybe put a voltmeter on it. :)
  4. PA5COR

    PA5COR Ham Member QRZ Page

    In any PSU where you will connect expensive equipment on, use a crowbar protection system

    My oldest supply with the L200 is the 80 amp PSU build for the 2 meter PA with 2 x the MRF 247 transistors build 25 years back wich both work fine till the day of today.

    I always put meters on my homebrew PSU's V and A meters, i like to check now and then what happens ;)
    With the PSU's come softstart (100 amps with .5 Farad condensators do bump ;) ), temperature controled fan(s) overdimensioned parts, like 200 amp diodes for the bridge rectifier etc.

    Have fun,

    Last edited: Dec 21, 2008
  5. WA7KKP

    WA7KKP Ham Member QRZ Page

    I've homebrewed a 13.8v power supply using a 317K and a pair of MJE2955 PNP transistors, in the classic PNP wraparound current boost.

    Simple, minimum parts count. Add a transistor and some current measuring circuitry, and you can have overload foldback.

    LM723 isn't that good as it is old technology. but they are cheap IC's compared to the 317T package.

    Gary WA7KKP
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