A500 rev.5 game port issue

[DownshiftDX]

Check the 74LS157 multiplexer (U15?) near the gameport. I had a similar issue on one of my A500s several years back and I tracked it down to that chip. Once I removed it, put in a socket, and replaced it everything was okay again.

[DownshiftDX]

Download the schematic and use meter to check track (and components) going to port from chips.

I had one with issues in past, turned out to be pin snaped inside port 2 socket.

On side note, you have tried reseating all chips? you can get some really wierd issues with dirty contacts.

I did mine in 2017. I was trying it blind based on reading I had done at the time somewhere on some old cached Amiga forums talking about the same problem. I'd already confirmed there was nothing wrong with continuity from the pins on the port to the chip. I didn't have a scope at the time to look at the outputs (not sure I would be able to make proper sense of it anyhow) so I just went for it as I was confident enough if my soldering skill to get the chip out without lifting anything and installing a socket.