Re: TECH: Ms. Pac Man reset problem

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The red button MUST RESET the CPU, if that is not happening then there is a
problem with the RESET circuit. Get that running and see what happens next.

At 07:09 PM 3/17/2001, you wrote:

>My Ms. Pac has a problem. The screen comes up as mostly dots. No sound, no
>gameplay.
>
>What I've measured:
> 4.93 volts on the TTL chips on the mainboard (slightly less on the aux
> board
>~4.91V)
> Reset line on CPU (Pin 26) is normally high... SW1 has no effect on
> CPU Pin
>26
> Pushing SW1 causes Pin 9 @ 9C to go low
> Pushing SW1 has no effect on Pin 15 @ 9C (it's LOW no matter what)
>
> 9C (74161) Measurements
> Pin 1 - changing state ( .466 Mhz )
> Pin 2 - changing state (varying frequency)
> Pins 3, 4, 5, 6 - high
> Pin 7 - changing state (1.5 - 3Mhz)
> Pin 8 - low
> Pin 9 - high
> Pin 10 - high
> Pin 11, 12, 13, 14, 15 - low
> Pin 16 - high
>
>I've narrowed the problem down to 9C or one of it's inputs (I think). I'm
>hoping someone with more knowledge and experience will comment on the above.
>Pin 2 @ 9C's input seems very strange to me.
>
>Thank you very much.
>
>Below I've included pinout of the 74161 chip.
>
>74161, 40161
>4-bit synchronous binary counter with load, asynchronous reset, and ripple
>carry output.
>
> +----------+
>/RST |1 +--+ 16| VCC
> CLK|2 15| RCO
> P0 |3 14| Q0
> P1 |4 74 13| Q1
> P2 |5 161 12| Q2
> P3 |6 11| Q3
> ENP |7 10| ENT
>GND |8 9| /LOAD
> +----------+
>
>
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Received on Sat Mar 17 20:00:24 2001