Re: KA7500 vs TL494

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