On Sat, Apr 14, 2012 at 2:12 PM, Dave Caroline <dave.thearchivist at gmail.com> wrote: Not healthy, that's for sure. Yes, but that "random" pattern isn't random enough. All of those chars are inverse, and that's not part of the Character ROM, that's an actual inverter (PETs had a 2K plain-only ROM, VIC-20 and C-64s had 4K ROMs with both plain and inverse characters encoded). That's also a distinct possibility. Which version of Static PET do you have? They came with different types of ROM and RAM (the schematics for all three variations are posted on zimmers.net). Main memory and video memory use the same chips, 1Kx4 in pairs. You need two working chips for video memory at at least 4 working chips for main memory (the first 1K is taken up with zero page variables, stack, and tape buffers). 2114 SRAMs are notoriously suspect, but 6550s can fail too. Before worrying about RAMs, check your Vcc... there are 4 regulators and 4 legs of +5VDC. If you've lost one, obviously, it will act strange. -ethan