A playfield magnet does not work, its fuse is blown, or the magnet locks on at power-up after the fuse is replaced.

Last Action Hero / Guns N' Roses: magnet dead or locked on

Cause: One or more of the three MOSFETs on the small under-playfield magnet board has failed, often with the 74HC273 that drives them. Cracked joints on the board's header pins (especially the return pin) are also common.

Checks

• Check the three 3 A slow-blow fuses beside the magnets under the playfield.
• Test the MOSFETs on the magnet board.

Fix

• Rebuild the whole board: socket the 20-pin 74HC273 (74LS273 or 74HCT273 also work) and fit new IRL540 MOSFETs in all three places, keeping the heat sinks.
• Reflow the .156" header pins on the board.

Systems

• Data East/Sega CPU Version 3b

Games

• Guns N' Roses
• Last Action Hero

Related tips

• Guns N' Roses: magnets blow their 2.5 A fuse in multiball
• Magnet driver MOSFETs on Last Action Hero and Guns N' Roses
• Rectifier board and playfield fuse ratings
• Whitestar flipper weak or dead after a MOSFET swap: fake part, test with TPL1
• Guns N' Roses magnets dead or locking on
• Logic-level MOSFET equivalents: 12N10L, 20N10L, 22NE10L, IRL530, IRL540
• Spare MosFETs for the driver boards
• Logic chips worth stocking

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)