The match number lights correctly and the knocker works for specials, but a matching number never awards a credit or knocks.

Match lights work but a match gives no credit: dirty Jones plug in the match path

Cause: A poorly contacting pin in a Jones plug somewhere along the match circuit (the path runs back and forth between head and cabinet). Plugs that were cleaned once can still be bad.

Checks

• Follow the match path on the schematic: score reel switch, score motor switch, match select, game over relay and credit select.
• Use divide and conquer with a meter, jumpering any switch that is normally open.
• Watch the actual ohm reading rather than the continuity beep: other circuits can leak enough to make a bad path beep.

Fix

• Clean the Jones plug pins and sockets properly and re-tension the sockets.

EM games have line voltage in the cabinet; unplug the game before working on plugs.

Systems

• Electro-mechanical

Games

• Old Chicago

Related tips

• EM feature dead: dirty interconnect plug

Source: Pinball Repair help group!! (Facebook group)