Re: KA7500 vs TL494

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.
>
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.

As you say, KA7500 specific notes are nearly non-existent; other than
this circuit schematic of an application available at DiodeGoneWild [1]:

    <https://danyk.cz/s_atx01h.png>

The switch supply section at his website is worth a look:

    <https://danyk.cz/index_en.html>

The Badcaps SMPS forum is also worth a look:

<https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-power-supplies-and-power-supply-design>

Note.

[1] <https://www.youtube.com/channel/UCQak2_fXZ_9yXI5vB_Kd54g>

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.