One row of the lamp matrix looks lit all the time (it actually pulses fast). With the lamp connector unplugged they all go out, and pressing the plug to one side makes every lamp behave normally. It happened with a brand-new replacement CPU board.
A row of lamps stays on solid, works if the plug is pushed sideways: repin the header
Cause: A poor contact at the lamp matrix connector where it plugs into the CPU board: repinning the cable-side plug alone did not help, so the header pins on the board were at fault.
Checks
- Wiggle or side-load the lamp connector at the CPU board while watching the lamps in lamp test.
- Repin the cable-side connector first; if the fault stays, look at the solder joints of the header pins on the back of the board.
Fix
- Replace (or reflow) the lamp connector's header pins on the CPU board, even on a new board.
Systems
Games
Related tips
- Brand-new replacement CPU board won't boot: press the socketed PIAs home
- A whole row or column of lamps is stuck on and extra bright
- How the CPU-controlled lamp matrix is wired
- Lamp matrix fault with good transistors: check R55 to R62
- Lamp row still dead after a new TIP122
- Test each lamp row driver with a test lamp
- Check the lamp matrix outputs with a logic probe
- Quick lamp row check: ground the row transistor tab
Source: Pinball Repair help group!! (Facebook group)