Fake lm338s

Discussion in 'General Electronics Chat' started by Jarrod1024, Apr 30, 2013.

  1. Jarrod1024

    Thread Starter New Member

    Apr 30, 2013
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    Hi, I recently ordered some lm338s from eBay, I had previously set up a lm317 circuit on my breadboard so I just replaced the lm317 with the lm338 but with a 22v input I can Only go down to 19v and the lm338 gets hot even with no load.
    The lm317s worked perfect in this circuit, are these lm338s fake?
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Check in the LM338 datasheet for the pinout! ;)
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Both devices have the same pinout, so if you wired it the same way it should work.

    I searched for the part on EBay, got some curious Chinese hits where the parts have a logo that may be mistaken for the National Semiconductor stylized N but are really something else.

    To be "fake" they have to say they are something they are not. I think this may be misleading packaging.

    They are about twice the price at Digikey. USPS shipping is about $2.50 with 2-3 day delivery.
     
  4. Jarrod1024

    Thread Starter New Member

    Apr 30, 2013
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    0
    I think I'm going to order some from digikey then, is there any difference between the lm338t/nopd-nd and lm338t-nd? Also should an lm338 get warm at all with the output not connected to a load?
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    "lm338t/nopd-nd" comes up blank in DK's search engine.

    These parts should not get warm at all with no load.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Check the pinout and stop wiring them up wrong!

    If it says LM338 it's an LM338.
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    You say you bought these on ebay? Check the seller's rating. Read the customer reviews. If the seller has any less than 95% positive reviews, either read the comments left for the seller to see if you think it's worth the risk, or find a more trustworthy buyer.

    Matt
     
  8. KrisBlueNZ

    Member

    Oct 17, 2012
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    14
    If "nopd" is a typo for "nopb" then it refers to a lead-free (no Pb), i.e. RoHS-compliant, version of the device.
     
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