On Thu, Sep 28, 2017 at 11:15 AM, Gerrit Heitsch <gerrit@laosinh.s.bawue.de> wrote: > On 09/28/2017 10:26 AM, Francesco Messineo wrote: >> >> On Thu, Sep 28, 2017 at 12:17 AM, Ethan Dicks <ethan.dicks@gmail.com> >> wrote: >>> >>> On Wed, Sep 27, 2017 at 4:24 PM, Francesco Messineo >>> <francesco.messineo@gmail.com> wrote: >>> >>> If the inputs are good and there's no good output, this is a good >>> candidate. It definitely has a lot to do with selecting the right >>> data at the right time. >> >> >> indeed UF6 was in a really bad shape. I've substituted with a good >> 74LS157 and now >> the video ram gets written correctly. >> The petester image shows a lot of bad DRAM and the video circuitry is >> still not working good: >> on every 8 columns, starting from the first, the character shape >> flickers. I have excluded the chargen ROM, but I need to go back to >> the schematic to understand what may be the problem here. > > > If the char ROM is good, take a closer look at the surrounding circuit. > There should be a 74166 or 74165 shift register somewhere that serializes > the output from the char ROM. If one of its inputs is bad, you'll get > vertical bars or flickering every 8 pixels. > > If you mean every 8 chars you have the whole char flickering, you should > look at the address counter for the screen memory access. it's every 8 chars. Now I first have to replace the UD9 socket (I hope). After swapping the EPROMs a few times, the PET no longer execute anything, so I guess it's that crappy socket. I'll have a look at that counter after I fix the ROM problem (unless something else died). > > Gerrit > > > > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2017-09-28 11:00:03
Archive generated by hypermail 2.2.0.