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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: KA7500 vs TL494
Date: Wed, 09 Apr 2025 09:42:22 -0400
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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).

The only thing a customer can do is avoid suppliers whose products 
are not proven reliable. Even rumours of such a condition can put 
a name brand out of business - hence the plethora of short-lived
off-shore vendor names in this market (and the bargain pricing).
>
>
>> Case in point is a 5V 40A unit advertised 'for use in LED sign',
>> commonly used in Onbon product. In the application where a repair
>> or replace decision was made, actual consumption was in the 35W
>> range, though a test sequence could draw much higher power.
>> replacement with an identically rated unit was Cdn$22.00.
>> 
>> The replacement was physically and schematically identical, but
>> relaid as a mirror image for component placement. Different
>> brand name.
>> 
>> Anyways - a basic self-oscillating bipolar transistor half bridge
>> with forced beta, synchronized/steered and pwm'd by opening and
>> shorting the resistor-limited, center-tapped 'drive' winding.
>> Open collector drive out of a KA7500.
>> 
>> What's a KA7500 ? Turns out to be pin compatible to TL494, but
>> mfrd by Samsung/Fairchild/ONS.
>> 
>> http://ve3ute.ca/query/TL494_vs_KA7500.pdf
>> 
>> Oodles of data and apps for the 494, not so much for the 7500.
>> If anyone's got app info published for the KA7900, in any
>> language, I'd be interested to see it.
>> 
>
>You mean a datasheet? It's here:
>
>https://www.mouser.com/datasheet/2/149/KA7500C-89501.pdf?srsltid=AfmBOoqgRNYOTol-O6pVSUwQ0v07-Tqdgmcnph3f_Uq5xj18Tvq5uAYY

No, I don't mean the data sheet.

RL