Apple ColorLaserWriter 12/600PS - Manual (Page 174)

10 Slide the controller board back into the printer.
11 Replace the two screws that hold the controller board in place.
12 Turn on the printer.
The printer does self-diagnostic tests each time it is turned on. During this
testing, the printer verifies the amount of memory installed. If the test
determines that a SIMM is faulty, specific status panel lights come on.
Try reinstalling the SIMMs, following the instructions earlier in this chapter.
If this does not resolve the problem, contact an Apple-authorized dealer. (For
more information about diagnostic tests and status lights, see Appendix G.)
M C
Y Bk
!
Cyan toner light on One light on means the SIMM in J11 is faulty.
Two lights means the SIMM in J10 is faulty.
Paper Out and Paper Jam lights blinking
149 Installing Options