Make sure mouse is in port 1
, if that's not the problem. Have a look for a spare U15
74HCT157 or possible the U4 8362 (Denise) might be broken.
Other than that U3 8364 (Paula), and U7
CIA, 8250 is also involved.
I would suspect the U15 chip because thats where the
Vpulse, Hpulse, VQpulse, HQpulse passes through before entering U4.
A simple test is to use a joystick, and if forward/back/left/right in port 1 won't work inside a game designed for a digital joytstick in port 1, there will be problem getting the mouse to work as well.
(related
thread,
schematic A500)
