[Premium-Rx] WJ8888 wonder radio

[Carcia, Frank A. HS]

    YUPPER! Here is a guy who knows! You don't get 1 mv of ripple with a
three terminal unit. We built
    5 volt 20 amp power supplies with about 2 mv of ripple at load. This
could be a big issue in a synthesizer.
 
fc

-----Original Message-----
From: John Perlick [mailto:p at mn.rr.com]
Sent: Tuesday, June 17, 2003 11:26 AM
To: Carcia, Frank A. HS; GandalfG8 at aol.com; premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] WJ8888 wonder radio


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 <mailto:francis.carcia at hs.utc.com>  
To: 'GandalfG8 at aol.com' <mailto:'GandalfG8 at aol.com'>  ;
premium-rx at ml.skirrow.org <mailto: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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