Re: Need help with an Atari Pong board

Thanks for the replies Gary and John. Yes it turned out that the 74L93
chip was too slow for even ol' Pong. :) I should have checked the specs
out. I was leaning towards John's idea at first thinking maybe the clock
signal wasn't right.

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. The
vertical was fine. I hooked it up to a Commodore 1085S monitor and it
looked and played fine except for the ball, which looked a little out of
sync, but that may be a symple sync issue with the monitor. Once I get my
1975 B/W tv from ebay delivered I'll hook it up to that and check.

The original hitachi TV was too thrashed (like someone had dropped it a
couple of time) and it was ugly. I got another tv that looked very "Pong"
to me.
http://games.rossiters.com/Pong-tv.jpg

It's an RCA 12" Model #A8122N. I know that I'm going to need to modify it.
 Does anyone have a book of TV schematics that has this model?

Thanks again Guys!

Matt

On Sat, 19 Jul 2008 16:03:33 -0500, solarfox@triluminary.net wrote:
> On Sat, 19 Jul 2008 12:39:20 -0700, you wrote:
>
>>I replaced the 7493 IC's with new 74L93 IC's (Not 74LS93).
>
> I think this is your problem. The 74L93 is too slow for this circuit;
> F8 is being clocked at 7.159MHz, and according to my TTL Databook, the
"L"
> version of the 7493 has a maximum fCount frequency of 3MHz. By
> comparison,
> both the base 7493 part and the 74LS93 are rated up to 16MHz on the CLKB
> input. (32MHz on CLKA, so if QA is tied back to CLKB then the whole
4-bit
> count can be run at 32MHz; they specify them separately because if you
> were
> trying to use the CLKB-driven section only, to make a 3-bit counter, you
> could only clock it at 16MHz.)
>
> In general, you have to be very careful about substituting an
> "L"-family part for a standard TTL, or even an LS part; 74Lxx logic is
> *much* slower, and it has much lower current-output capability.
>
> Put a proper 7493 in there, and see if that doesn't produce more
> positive results. :)
>
>
-----------------------------------------------------------------------------
> "In ancient times, they believed that there were only four kinds of
> matter:
> Earth, Water, Air, and Fire. Nowadays, of course, we know that there are
> actually four states of matter: Solid, Liquid, Gas, and Plasma. Thank
God
> for progress!" ---(Kelvin Throop III)
>
-----------------------------------------------------------------------------
> solarfox@removethis.triluminary.net (Gary Akins
> jr.)
>
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>
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Received on Sun Jul 20 01:00:39 2008