Re: Commodore PET 4016
Oh well it's a pity the CharGen ROM has now failed, but at least you may now have found the issue.
It does seem like your 'scope is mis-reading 12V as 9V, if you get the same on the 4032 / your DMM reads it as OK.
I wonder if the 'scope input is being over-loaded and is clipping? - What is it's max. input spec / have you got a x10 probe?
BTW, I spotted a 4032 that was sold (before I saw it), at yesterday's annual BVWS Retro-Tech event. I'm not sure what it sold-for, but it had an interesting label (maybe now not too readable, after compression) on it that may give a clue that it wasn't from a School but a major organisation - See attached.
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