The bank error board is a lot closer to working since if it got that far, almost every other part tested OK. If you are completely sure that it's none of the traces on the page or my post, can you probe the NEO-D0 pin with any 1991+ game inserted and see if you get any pulsing? It should pulse frequently when a song is supposed to be playing for example.
The other board is in a worse spot since the Z80 is possibly not running at all. There's more to check for (Z80 clk should pulse, RD/WR/IO signals should be pulsing, SM1/RAM/NEO-D0 traces between Z80 should be checked etc....). I'd like to make a full writeup on everything to test but there's a lot of info on the wiki currently. Pretty much any Z80 connection excluding the cart slot is potentially the cause. What have you tried so far?
The other board is in a worse spot since the Z80 is possibly not running at all. There's more to check for (Z80 clk should pulse, RD/WR/IO signals should be pulsing, SM1/RAM/NEO-D0 traces between Z80 should be checked etc....). I'd like to make a full writeup on everything to test but there's a lot of info on the wiki currently. Pretty much any Z80 connection excluding the cart slot is potentially the cause. What have you tried so far?