UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

SiriusHardware · 17th Mar 2021, 9:35 pm

From #1111, system RAM looks like it is being written to (pin 19 active) but not read from at all (pin 1 inactive) - or the signal which should be driving pin 1 low is missing in action, possibly. Of course we don't know exactly where the CPU is stuck or what it is trying to do.

Try monitoring UI10 / pin 1 for activity in the period immediately after reset and seeing if there is any activity on it then. If we never see any attempt to write to system RAM there may be a problem with the circuitry that generates the write signal for the system RAM.

17th Mar 2021, 9:35 pm	#1113
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,556	Re: Non-working Commodore PET 3016 From #1111, system RAM looks like it is being written to (pin 19 active) but not read from at all (pin 1 inactive) - or the signal which should be driving pin 1 low is missing in action, possibly. Of course we don't know exactly where the CPU is stuck or what it is trying to do. Try monitoring UI10 / pin 1 for activity in the period immediately after reset and seeing if there is any activity on it then. If we never see any attempt to write to system RAM there may be a problem with the circuitry that generates the write signal for the system RAM.