It has recently been found out that on B boards 93646B-3 and 93646B-4 there is a suspected routing error for one of the pins from PAL 3.
This means that if you are doing a game conversion using on of these B boards, you cannot natively use the BGSB3G PAL chip, you will have to either lift pin 9 of the PAL and solder a wire to C13 of connector CN3 or use PAL BGSB3F, lift pin 7 and solder a wire to C13 of connector CN3.