Yup, I always test to the shoulder of the chip pin. I've taken out the ROMs and checked them and the sockets (the sockets are pretty new, I replaced them all when cleaning up the corrosion). Just in case I cleaned the ROM legs with IPA and a fibreglass pen. I'll try another set of ROMs just in case.DId you continuity check from IC29..31 LEGS to the rom LEGS? I highlight LEGS here because often a fault can be between socket and chip leg - it's important to probe the actual chip. And use as little force as possible -- I've experienced failures where the pressure of the probe is sufficient to make the contact, then it doesn't work again without probe pressure.
It's also possible you do have a failing ROM - it does happen. I'd swap to another ROM set if you can.
IC29..31 can also fail after battery damage.
I don't think it's the address latches as presumably the walking of the ROM address lines relies on them ?
A while back I purchased one of the new replica A3000 PCBs as a way of supporting the project. I'm starting to think this machine might make a good donor to populate it!
Statistics: Posted by cjed — Wed Mar 19, 2025 1:40 pm