Two controlled inserts glow faintly all the time during play, with both incandescent bulbs and LEDs.

Two inserts faintly lit all the time: failed lamp driver SCR

Cause: A failed SCR on the lamp driver board leaks enough current to light the lamp. LEDs can glow on a very small leakage voltage even with the driver connectors unplugged, which makes the board look innocent when it is not.

Checks

• Confirm the inserts are in the lamp matrix and are not always-on GI lamps (see the lamp table in the manual).
• Do not rule out the driver board just because an LED still glows faintly with its connectors unplugged; test with an incandescent bulb or check the SCRs directly.

Fix

• Replace the SCR on the lamp driver board that drives the affected lamps.

Systems

• Bally MPU AS-2518-35

Games

• Granny and the Gators

Related tips

• One controlled lamp dead even after a new SCR: lamp driver board fault
• Controlled lamps flicker or stay out after fitting a replacement lamp driver with LEDs
• LEDs flicker in controlled lamps on Bally and Stern SCR lamp boards
• Substitute SCRs for the lamp driver board
• Lamp driver board layout: SCRs, decoders and connectors
• Lamp driver board: which SCR drives which connector pin
• A controlled lamp that is always on means a shorted SCR
• One insert lamp dead after nearby work: bad pin in the lamp driver IDC connector

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