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Old 22nd Feb 2021, 11:41 pm   #619
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 6,715
Default Re: Non-working Commodore PET 3016

It's still possible that a fault on the databus buffers is loading the unbuffered databus and stopping everything else on the unbuffered databus from working, so I think that ultimately the databus buffers are going to have to be replaced to rule them out. I think it's worth first removing as many of the unpluggable devices which are also on the unbuffered bus as we can to see if removing any of those allows the CPU to run.

It might be an idea to mark one of the 6520s with a paint dot or a sticky dot if they are not already distinctively marked in some way so that we always know which one was originally where. Unintentionally moving an (unknown) faulty device from one position to another could introduce a whole new level of weirdness, so for the time being we don't want any devices leaping from one place to another, even if they do have the same part number on them.
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