Re: Non-working Commodore PET 3016
Indeed, we should probably also have Colin check the RAS and CAS refresh signals going to each DRAM as well. Given the seemingly random pattern of IC failures we have found so far, it would be quite possible to have an as yet undiscovered fault in the refresh circuitry.
There was a recent discussion elsewhere on the forum about the relative merits of plastic vs. ceramic IC packages and there was some mention of plastic packages being prone to damage by moisture ingress. From the condition of the PROMs I have no doubt that the machine spent some time in a damp environment somewhere.
I've only belatedly realised there is no CS or CE pin on these RAMs so that's why the UI10 / UI11 buffers are there, to gate the connection between the RAM inputs/outputs and the buffered address bus.
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