Re: Broken P500 (was: Commodore 8296GD)

Hi,
 
I tested the PLA and it's good.. For those that don't know.. I also have an original working NTSC P500 to test/compare.
One other hypothesis is bad bank 1 ram. Again, soldered in, which always seems to be the reason I get stuck. 
 
Steve


>________________________________
> From: Michał Pleban <lists@michau.name>
>To: cbm-hackers@musoftware.de 
>Sent: Tuesday, October 2, 2012 3:03:31 AM
>Subject: Broken P500 (was: Commodore 8296GD)
>  
>Hello!
>
>Steve Gray wrote:
>
>> My P500 is not happy. I've tested all the socketed main chips and they
>> are ok. The voltages look ok. There seems to be activity in the system
>> but I'm not sure where it's going bad. I suspect the 6525 might be bad
>> but it's soldered in, and since my eyes are going bad I haven't been too
>> keen on soldering these days. A also need to convert it from PAL to
>> NTSC, which again will need some soldering.
>
>My P500 had recently gone bad too, and it exhibits similar behaviour to
>yours, including similar activity on address lines.
>
>I don't believe a broken 6525 would bring a system down like that - the
>system is still alive, but the CPU appears to have been lost in the
>address space. A broken I/O chip will not make it - for example, when
>CIA breaks down in CBM-II it simply brings the whole bus down and the
>CPU halts. After looking what might go wrong in the system, my bet is on
>the PLA chip. I will be working on it in some spare time...
>
>Regards,
>Michau.
>
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