My C128's are the same too. One it seems the Sid and Vic video circuit may have shorted components would I have to pull each component off and then how do I check resistors etc with a voltage meter? I have no scope at all. Terry Raymond On Sep 29, 2017 2:21 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: > >>> > >>>> > > > >>> > >> > >> If you have an older PET (without CRTC) that has been upgraded to Basic > 4.0, > >> the jumpers may not have been set correctly. There are jumpers that > >> control addressing of the ROMs. If they are not set correctly you will > have > >> addressing problems. Check the schematics for correct jumper settings. > >> > > > > Yes, I was just going to check that. I've noticed the jumpers don't > > match my 3032 (with older basic). The owner of this PET said it used > > to work though, so I was assuming that the jumper were correct. > > I will also change the timing resistor and tantalum capacitor on the > > 555 reset circuit, I've noticed the reset signal isn't very well > > behaved (it resets randomly and sometimes doesn't release the reset > > line). I think the tantalum capacitor is shorting randomly to ground > > or the 1M resistor is intermittent. > > Old hardware sometimes has lots of faults. > > 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. > > Frank > > Message was sent through the cbm-hackers mailing list > Message was sent through the cbm-hackers mailing listReceived on 2017-09-29 16:00:03
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