On Mon, Oct 2, 2017 at 9:41 AM, Francesco Messineo <francesco.messineo@gmail.com> wrote: > On Fri, Sep 29, 2017 at 10:20 AM, Francesco Messineo > <francesco.messineo@gmail.com> wrote: >> On Fri, Sep 29, 2017 at 7:55 AM, Francesco Messineo >> <francesco.messineo@gmail.com> wrote: >>> On Fri, Sep 29, 2017 at 7:05 AM, William Levak <wlevak@sdf.org> wrote: >>>> On Thu, 28 Sep 2017, Francesco Messineo wrote: >>>> >>>>> On Thu, Sep 28, 2017 at 12:48 PM, Francesco Messineo >>>>> <francesco.messineo@gmail.com> wrote: >>>>> >>>>>> >>> >>>>> > >> update: changing the UD8 socket, did bring the system to the basic >> prompt, with correct bytes free count. >> I then restored the two CAS resistors (I had lifted them to swap RAM >> banks) and now I have a completely black screen, not even the garbage >> screen if I remove the UD9 ROM :( >> Looks like I now have to debug the video signal path. This PET hates me I guess. > > another update (as I find time to look at it): pin 6 of UG11 is stuck > high (that's video output) but the inputs of that gate look fine (at > least they're toggling...). > When I find another 30 minutes left, I'll change that 74LS20 and see > what happens next. changing UG11 didn't solve the problem :( Pin 6 is always high, so now I must look for a timing problem, which is much worse. Signals on the input of that NAND gate have not the right timing anymore (at least one of the three) :/ Frank Message was sent through the cbm-hackers mailing listReceived on 2017-10-03 18:00:04
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