Just looking for some guidance on a board I’m repairing. U41 and U42 have some corrosion damage on their legs. I was going to clean board, socket the chips and replace. Are these a ROM type chip or a RAM type chip? I don’t have a chip reader/burner so I wasn’t sure if these are just an off the shelf type part or if I need to write something to them.
U41 and U42 are both 6821 peripheral interface adapters (PIA). These are common chips in the 6800 family, and are used as interface devices between the main processor (a 6801 in most cases) and the input/output devices (like the coils, and switch matrix). So they are neither RAM or ROM chips, and don't require any prep when replacing.
Let me just add that if you are replacing chips that have battery damage, they are somewhat difficult to remove without damaging the traces on the board. Your best bet is to use a small pair of clippers to cut the legs off the chips where they meet the plastic chip body. Then use a soldering iron to heat up each leg, and then pull them out one at a time with a small pair of pliers. Then go back and clean out the holes with a solder sucker. Board solder that has corrosion on it doesn't conduct heat well, so it may be best to try to heat up the legs from the backside (undamaged) side of the the board.
Good luck!
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