Some CPU-controlled lamps do not light, or stay lit all the time.
One or more controlled lamps never light or stay on
Cause: Burnt bulb, bad socket or wiring, a broken shared ground return, a failed lamp driver transistor, or the control board.
Checks
- Check the bulbs.
- Check the sockets and wiring; lamp ground returns are shared by groups of driver transistors on the driver board, so a broken return can kill a whole group.
Fix
- Replace bulbs or repair wiring; then suspect the driver board, then the control board.
Systems
Related tips
- How driver board lamp latches work
- Checking lamp signals during test step 16
- Driver board A3-J3 lamp groups and relays
- A display segment or digit is always on or always off
- A driver board output is stuck on or dead
- None of the CPU-controlled coils fire
- Some CPU-controlled coils are dead or locked on
- Driver board A3-J2 backbox lamps
Source: System 80 Service Manual, Gottlieb