OK, have taken off old modifications to coin door ,back to standard.still didn't start ,tilt switch in back box not contacting properly.cleaned and readjusted.Now goes!
When you turn it on from power point ,it lights up but tilt light on back glass is on!
Then you press game start,tilt light goes off,game resets score reels,pops ball into shooting lane,backglass says 1st ball(all good)
Now when you get bonus up to maxium(5000) the knocker  knocks a game,credit wheel goes to 1 game BUT THERES A BUZZING SOUND coming from credit wheel coils (2 of them).sounds bad so I turn pin off.Go through sequence again and does same thing...
It's like some switch or relays stuck? I don't know