Re: Need help with an Atari Pong board

Are you sure you have a good clock signal in? Have you used a scope or
logic probe to verify? A voltmeter won't work as a logic probe in this
circuit...do you have any image at all on the TV/monitor?

John :-#)#

Matt Rossiter wrote:
>
> Thanks everybody for helping me with I,Robot. As soon as I get the
> new parts in next week I will respond with an update.
>
> I'm also working on a Pong board. I fixed the power supply circuit
> and the clock circuit. I'm stumped with the horizontal counter circuit.
>
> I will refer to Dan Boris's excellent re-drawing of the Pong schematic
> here. http://www.atarihq.com/danb/files/PongSchematic.pdf
>
> (He gives a nice description of the horizontal counter circuit here -
> http://www.atariage.com/forums/index.php?automodule=blog&blogid=52&&st=25
> <http://www.atariage.com/forums/index.php?automodule=blog&blogid=52&&st=25> )
>
> 1) I've carefully replaced all of the IC's in this circuit and
> inspected all the traces.
>
> 2) The Problem starts with F8 (7493) which is a 4-bit binary counter.
> Both the Master Rest Inputs are low (Pins 2 and 3) so it should be
> couting. The clock on pin 14 looks good to me. However I'm not
> seeing any pulses on the output pins 12, 9, 4, and 11. Each of the
> output pins have slightly different voltages between 1.5 to 3.5. No
> clock signal though.
>
> I replaced the 7493 IC's with new 74L93 IC's (Not 74LS93). It's such
> a simple circuit - I don't really know what else to check. I might
> add that when I first got the board, the +5v pull up
> resistor (normally soldered to the back of the board with a 250uf
> capacitor) was blown. Probably due to a voltage regulator failure - I
> have since fixed the power supply and replaced the resistor with a new
> 4.7k resistor. I wasn't sure what value was in there before since it
> was burnt.
>
> Looking for suggestions. :)
>
> Thanks!
>
> Matt
>

-- 
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Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
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