On Wed, Sep 27, 2017 at 8:41 PM, Ethan Dicks <firstname.lastname@example.org> wrote: > On Wed, Sep 27, 2017 at 12:13 PM, Francesco Messineo > <email@example.com> wrote: > >> well, the changes are really small, actually part of the same >> character changes (modifying the >> character itself), not the character. > > Ah... the pixels in a character cell are changing? That's really odd. > The path is the timing circuit reads the pair of 2114 RAMs that are > gated over to the CHARGEN ROM then the ROM's data outputs are hooked > to a shift register for the specific dot that's then sent up the > 6-wire cable (video, h sync, v-sync and 3 grounds). looks like UF6 is bad, it doesn't output the VRAM Write signal (TV RAM R/W), its inputs are correct, so I'm going to replace it. It might be bad on other signals too. > > If you have a petester ROM installed, then BASIC and the KERNEL ROMs > aren't a factor, but address and data buffers could be, or address > select logic. yes, I'm using petester since it cycles writing and reading to VRAM so it's easier to probe around. Let's see what happens when I replace UF6. Frank Message was sent through the cbm-hackers mailing listReceived on 2017-09-27 21:00:02
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