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

SiriusHardware · 8th Feb 2021, 4:22 pm

On that one, chip select pins 18, 20, go to 0V and pin 21 to +5V. Power supply pins are pin 12=0V and pin 24=+5V.

As pin 18 is a chip select rather than A11 on that IC, that suggests it is a 2K ROM, so reduce the max read address to 2048 and don't connect the A11 output from the Mega / Pi to pin 18 on the PROM.

8th Feb 2021, 4:22 pm	#529
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,575	Re: Non-working Commodore PET 3016 On that one, chip select pins 18, 20, go to 0V and pin 21 to +5V. Power supply pins are pin 12=0V and pin 24=+5V. As pin 18 is a chip select rather than A11 on that IC, that suggests it is a 2K ROM, so reduce the max read address to 2048 and don't connect the A11 output from the Mega / Pi to pin 18 on the PROM.