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    Getting old and out of touch

    ShawnR

    Member
    Hi All

    I graduated from college in 1984. I worked for several years in electronics but then diverted to unrelated. I continued to dabble....but knew I was losing ground quickly as electronics advanced.

    Today, I was on the bench and the power supply I built several years ago, just a common LM350K based supply, failed. Going to Digikey to get a new regulator, found it to be obsolete unless I buy 50 and then they are $85 plus, each. Searching for TO-3 case regulators, wow....everything I was familiar with seems changed.....

    Sooo, what is the norm these days? I found LM338's in a TO220 case, that should work, or go to a 317, reducing the available current to 1 Amp.


    What are hobbyists using for variable power supplies?
    Any suggestions?

    Feeling old....;-)
     

    Diver300

    Well-Known Member
    Most Helpful Member
    The TO-218 package will fit in the place of the T0-3 package.

    I think that the TO-218 was designed to be like that.

    I have no idea if there is TO-218 packaged regulator that would work, but you could use a transistor and mount the control electronics elsewhere.
     

    ShawnR

    Member
    The LM388 will give you 5A or use the LM317 with bypass transistors for increased current?
    You mean LM338? $ 121 ...ouch


    I might have to rework the installation, going with a TO220 case component and a bypass transistor. Something I have thought of for other projects but never actually done.

    Thanks
    Shawn
     
    Last edited:

    Pommie

    Well-Known Member
    Most Helpful Member
    Just had a look at prices. Didn't realize they were so expensive. Over $100 for a TO3 version. Looks like I'm out of touch too.

    Mike.
     

    ShawnR

    Member
    Thanks Mike
    I ordered some. I have not looked at ebay for years for stuff. Expected delivery is 1-2 months but I can get by. I am not doing much these days, obviously, anyways.
    Cheers,
    Shawn
     

    KeepItSimpleStupid

    Well-Known Member
    Most Helpful Member

    ShawnR

    Member
    Thanks KISS

    I am in Canada and international shiipping rates would be a lot. If COVID had not caused the borders to be closed, we would normally drive 30 minutes to Minnesota and bring it in, saving customs fees. But, we cannot even cross the border now. Nice to see reasonable prices for those components. If anyone likes them, might be a good time to stock up.
    Thank you
    Shawn
     

    sagor1

    Active Member
    Shawn, be careful of the Chinese LM338K, often they are fake. They put a LM317 inside a metal can and re-label it assuming no one will pull 4A or 5A thru it. Test them carefully, make a circuit with the LM338 on a good heatsink and pull 2 to 3A thru it, see if they survive.
    I'm glad I saved all those socketed LM338K pulls I have. If you want to pay postage for a couple free originals (working pulls) from Ontario, contact me off list.

    Steve
     

    gophert

    Well-Known Member
    Most Helpful Member
    ShawnR
    What current and voltage are you looking at? You might want to consider a switch mode power supply (Dc/Dc converter). Much less heat to deal with. Modules are available for very low prices.
     

    Beau Schwabe

    Active Member
    The closest equivalent to the LM350K in the same package is the NTE970 for $18 and change from Digikey. The pin out is the same between the two. Note: if you look at the datasheets one has the bottom view turned 180 from the other... but yes, the pin outs are the same, and the characteristics are the same with an improved output overhead voltage with the NTE970 of 33V versus 25V with the LM350K. Input voltages are the same ( 35V) and current is the same (3A)

    364 in stock as of 10-26-2020

     

    ShawnR

    Member
    Thanks everyone. Since I have the ebay ones ordered, I will wait to see what happens. It is just the variable side of my multi output power supply. I can get by with the fixed 5 and 12 v outputs.

    Regards
    Shawn
     

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