Pressing start gives a "pinballs missing" type message, a drained ball doesn't end the ball, or random multiball happens; balls stop part way down the trough.
Balls hang in the trough: divots in the trough metal
Cause: Balls wear small nicks in the V of the trough where each ball rests (often a pair per ball position), and the balls hang on them. The spot where balls drop in is a lesser problem. Applies to the gravity troughs used from Indiana Jones to Cactus Canyon.
Checks
- Remove the trough and look along the V for small nicks at each ball resting position.
Fix
- Grind the nicks smooth with a rotary tool or hand file, then sand the sides of the V with 220 or 320 grit.
- If that fails, fit a new trough, A-16809-2, which wears less.
Systems
Related tips
- Random multiball or game never ends on early opto troughs
- "Pinball Missing" message
- "Pinball Missing" message
- Balls hang in the trough and none is served: divots in the trough floor
- Random multiball from cracked blue resistors on trough boards
- Old and new WPC ball trough designs
- Opto ball troughs from Indiana Jones on
- Two balls served at start and the lock spits its ball out: count the balls
Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)