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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: KA7500 vs TL494
Date: Sat, 12 Apr 2025 15:08:18 -0400
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On Wed, 09 Apr 2025 08:51:52 -0700, john larkin <jl@glen--canyon.com>
wrote:

>On Wed, 09 Apr 2025 09:42:22 -0400, legg <legg@nospam.magma.ca> wrote:
>
>>On Tue, 8 Apr 2025 21:22:37 -0700, Joerg <news@analogconsultants.com>
>>wrote:
>>
>>>On 3/25/25 6:25 AM, legg wrote:
>>>> Chinese commodity power supplies have tended to use recognizable
>>>> configurations from times gone by. In doing so, it's easy to
>>>> miss some of the 'small stuff' that actually produced a reliable
>>>> product, in the day.
>>>> 
>>>> Even more so, when pricing reaches the 'replace vs repair' threshold
>>>> - why even bother with burn-in, in that case? If no burn-in or field
>>>> return failure analysis is ever consudered, the small errors persist,
>>>> particularly if vendors play wack-a-mole with the same hardware
>>>> offered under different brand names and paperwork.
>>>> 
>>>
>>>Burn-in? Doesn't that happen at the customer? :-)
>>
>>No, burn-in is a well-defined process control step used in the 
>>manufacturing of equipment to achieve and maintain low failure 
>>rates (ppm).
>>
>
>What fraction of the parts and equipment that you buy has been
>burned-in? And how do you know?
>
>I'd expect 0%, and that you don't know.

Purchases of assembled hardware, here, are generally consumer 
grade, with no obvious indication that infant mortality has 
been addressed. 

Some incoming aql levels are specified in the data sheets at 
the component level. Things like pumps, motors and power supply 
units are included in this category.

Designs or products that go out the door can only achieve ppm 
failure rates if a burn-in strategy is included after final assy.
Nuts and bolts can fail just as often at this stage.

RL