I can’t get a 286 to post. There is no corrosion. The board only has ISA slots. After trying two ISA/PCI POST cards, all I get is an unlit IRDY LED, although it is unclear if the IRDY signal only refers to PCI signals. (Searches for IRDY error only results in discussions about POST cards.) There are no hex codes displayed. There is no signal on a known-working VGA card.
I’ve tried burning new Phoenix BIOS ROMS, tested all socketed 74 logic in a Mini-pro, checked clocks with an oscilloscope, see normal activity on two of the three CPU’s that I’ve tried, and am fast running out of options.
I’ve ordered a set of chip sockets, assuming that I will need to remove and test each soldered-in IC, as well as an eBay Motorola clock/BIOS setting chip, but if you can suggest anything that I can test before desoldering and likely butchering a lot of traces, I’d love to hear what procedures you might follow to troubleshoot mainboards.
I’ve tried burning new Phoenix BIOS ROMS, tested all socketed 74 logic in a Mini-pro, checked clocks with an oscilloscope, see normal activity on two of the three CPU’s that I’ve tried, and am fast running out of options.
I’ve ordered a set of chip sockets, assuming that I will need to remove and test each soldered-in IC, as well as an eBay Motorola clock/BIOS setting chip, but if you can suggest anything that I can test before desoldering and likely butchering a lot of traces, I’d love to hear what procedures you might follow to troubleshoot mainboards.