Re: Asteroids Vector RAM Read/Write Problems

Well I'm certainly no expert on these things. But If the selects are
toggling, and Vector Rom reads out good. Then I would suspect bad ram on M4
or R4 or both.

Kevin

On Sun, Jan 23, 2011 at 1:16 PM, Dave Langley <
dave2084.forums@googlemail.com> wrote:

> Yes, as far as I can tell both pairs are being correctly enabled when I
> RAM test the approprate range using the 9010A. I might confirm the signals
> look got on my 'scope though just to be sure.
>
> 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 17:48:27 2011