Is the /ram being selected? Chips L3 pin 12, M5 pin 4, and 6?
On Sun, Jan 23, 2011 at 2:30 AM, Dave Langley <
dave2084.forums@googlemail.com> wrote:
> I'm trying to fault find an asteroids board with Read/Write Problems on
> the vector RAM.
>
> So far I've done the following:
>
> The game arrived with no display and two tones indicating E2/E2 RAM Fault;
> I quickly traced the fault to M5 pin 11 being stuck low so the RAM was never
> selected.
>
> Now the game gives two high tones and two low tones. When using my Fluke
> 9010A I am getting a R/W error on bits FF for all addresses in the range
> 4000 to 47FF. The vector ROM however gives the correct checksum (CBED) so
> the buses must be OK?
>
> Does anyone have any idea where I can go from here?
>
> --
> Dave Langley
>
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Received on Sun Jan 23 14:01:32 2011
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