Re: Need help with an Atari Pong board

On Sat, 19 Jul 2008 22:00:33 -0700, you wrote:

>At a quick glance I couldn't see that I had any 7493 or 74LS93's on hand
>but I did have some 74HC93's on hand and the specs looked faster. Sure
>enough I got clock signals finally in the Horizontal sync circuit.

        I'm actually a bit surprised that worked. HC means "High-speed CMOS";
usually, mixing CMOS and TTL is asking for trouble, due to the differences
in voltage thresholds between what they consider "high" and "low". (The
74HCT family, "High-speed CMOS TTL-compatible", was made specifically for
this reason, to allow direct substitution of CMOS parts in existing
TTL-based designs.)

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solarfox@removethis.triluminary.net (Gary Akins jr.)
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Received on Sun Jul 20 10:24:38 2008