I'm new t the pinball world and this is my first post ever so please be gentle with me if I'm asking a stupid question or posting at the wrong sub-forum.
Here is the thing: I have a dirty Harry (bought it a month ago worked very hard to bring it to a very good state).
When I put it in a switch test mode, Column 1 switches 1-7 (but not switch eight) "flicker" for a fraction of a second every 2-3 seconds. If the single switch tested at the time belongs to column 1 you see it on a close state each time the column flickers.
Actually this doesn't effect anything in the machine. Except when I try yo enter initials after high score: You can scroll through the letters with the flippers but letters are entered as if the start button was pushed randomly (this what made me look for a problem on the first place).
When I disconnect J207 and J209 the problem disappears - so i assumed it's not a board issue. Nevertheless I replaced U20 - it didn't change anything.
I've examined all column 1 switches visually for problems and examined connectivity between all of then but everything seems just fine.
I don't know how to continue. I'd appreciate any suggestion