Re: KA7500 vs TL494

On Sat, 12 Apr 2025 13:07:19 -0700, john larkin <jl@glen--canyon.com>
wrote:

On Sat, 12 Apr 2025 15:08:18 -0400, legg <legg@nospam.magma.ca> wrote:
>

On Wed, 09 Apr 2025 08:51:52 -0700, john larkin <jl@glen--canyon.com>
wrote:
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On Wed, 09 Apr 2025 09:42:22 -0400, legg <legg@nospam.magma.ca> wrote:
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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

>
With modern electronics, burnin isn't necessary or feasible.
>
Temperature cycling and vibration would improve reliability a bit, but
that's not practical either.
>
The biggest failure cause is bad engineering.
>
Modern electronics, except for the obvious cheap junk, is remarkably
reliable.

Apart from the price, there's nothing 'obvious' about modern
electronic reliability. Modern's got nothing to do with it.

Off-shore hardware can suffer 200% tarrifs and still be
competative at the retail level. There's plenty of room
for quality control.

Those margins are, instead, being absorbed by shareholders;
hence the stock market sensitivity at that end.

RL