WPC switch column issue

Banzaipinabll

Active Member
Aug 16, 2011
432
205
43
Aberdeen
Being a bit lazy, hope someone can help without me doing to much digging.

WPC CPU, one switch column is out, checked and know its a cpu issue. Changed U20 IC and same issue remains.

Idea quick idea's before I dig into fault finding
 
OP
OP
Banzaipinabll

Banzaipinabll

Active Member
Aug 16, 2011
432
205
43
Aberdeen
Got a column of switches not working, pin 6 on J207. Have confirmed issue is on the board.
Changed U20 and U14, no change
Logic probe all the areas as detailed on pinball wiki.
When logic probe I get a high reading on all the pins including pin 6. However pin 6 gives a solid tone, the other give the same tone, but the tone is pulsing. Is the difference an issue, I get the same tone difference at U20

Any help please