[Premium-Rx] WJ8888 wonder radio

[John Perlick]

I agree, the 723, in a properly designed circuit, is very reliable...at least as reliable as an LM340.  The problems come from bad designs.  BUT, the 723 is used in radios because it's noise output is typically 100X lower than a three-terminal regulator in a good design.

John
K0UM
  ----- Original Message ----- 
  From: Carcia, Frank A. HS 
  To: 'GandalfG8 at aol.com' ; premium-rx at ml.skirrow.org 
  Sent: Tuesday, June 17, 2003 9:54 AM
  Subject: RE: [Premium-Rx] WJ8888 wonder radio


      Many years ago I worked for a power supply company. We shipped hundreds of power supplies a week.
      The 723 worked great for us but we never ran high voltage on them or excessive current. I think problems
      crop up when someone forgets to use the proper pass device and hopes the chip does both jobs. 
      Yes today there are very nice fixed regulators but thermal is still the same issue with high unregulated
      input voltage. I know of a large number of 723s over Iraq that performed very well and some of them are 20
      years old. fc  
    -----Original Message-----
    From: GandalfG8 at aol.com [mailto:GandalfG8 at aol.com]
    Sent: Tuesday, June 17, 2003 10:37 AM
    To: premium-rx at ml.skirrow.org
    Subject: Re: [Premium-Rx] WJ8888 wonder radio


    I have to agree with Richard on this one.
    The 723 may be versatile, and convenient to use, but it is also notorious for being unreliable.
    I've experienced more problems with PSUs based on the 723 than with any other integrated circuit regulator.
    They don't have to be run outside their limits or in any way overstressed either for failures to occur.
    The general failure mode seems to be catastrophic.
    However, I've also seen them apparently continuing to function but with the output voltage drifting up over a period of time despite the peripheral components remaining in tolerance.
    This can still have some pretty severe consequences in more basic PSUs without proper over voltage protection.
    I would never recommend the 723 for new designs and, unless there's a very real desire to keep something original, would strongly suggest replacing any 723 based circuits with one of the many, and more reliable, alternatives.
    regards
    Nigel
    G8PZR






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