Broken P500 (was: Commodore 8296GD)

From: Michał Pleban <*lists_at_michau.name*> Date: Tue, 02 Oct 2012 09:03:31 +0200 Message-ID: <506A91C3.4030201@michau.name> · lists_at_michau.name

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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