WRT to the 6525, a bad one can 'black screen' the system. The one that handles the keyboard also controls the 16k bank that the vic-ii sees. When I got that batch of 6525's a few months ago I did not have a socketed 6525 in any of my cbm-ii machines to test with but I now have a P500 with a socketed 6525 and I know that some of the bad ones will stop the machine from visibly booting. rob On 02/10/2012 17:07, Steve Gray wrote: > 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 <firstname.lastname@example.org> > *To:* email@example.com > *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. > > Message was sent through the cbm-hackers mailing list > > Message was sent through the cbm-hackers mailing listReceived on 2012-10-02 16:00:40
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