Both inlane and outlane switches and the drain switch never register, in game or in switch test, while the rest of the game works.

Inlane, outlane and drain switches all dead: blown switch transistor Q49

Cause: The dead switches share one CPU connector (1J8) and one switch driver. Here the 2N3904 switch transistor Q49 had blown (its body was visibly cracked), most likely from solenoid voltage getting onto the switch matrix at some point.

Checks

• Use the manual to find which connector and switch row or column the dead switches share.
• Check the resistor array for that line, then test the 2N3904 switch transistors on that circuit with a meter on diode test.
• Look closely at the transistors for cracked or missing pieces.

Fix

• Replace the failed 2N3904 transistor.
• Look for the cause of the original short (a switch touching a coil lug or a pinched wire) before putting the game back in service.

Systems

• Williams System 11A

Games

• Pinbot

Related tips

• Switch matrix dead after an under-playfield adjustment with power on
• Fixing a dead switch column on the CPU board
• System 11 switch matrix: connectors and chips
• Row or column error: CPU board or playfield?
• Flipper button resets the game or a slingshot tilts it
• Whole switch column dead and board fails the jumper test: column transistor
• Lamp and switch matrix transistor positions on the CPU board
• One switch column dead: parts to check in order

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