asked Dec 5, 2007 at 7:09pm
Apple Apple StyleWriter Pro

Apple Laserwriter Pro 600 unknown failure

Trouble-free for 14 years. It failed after replacing toner cartridge.
Symptoms at printer power-up:
• All four status lights come on briefly, then go out.
• Three yellow lights come on after a few seconds.
• Two yellow lights (paper out and paper jam) then remain on along with the green (in use/ready) light.
Diagnostic test run with DB-9 pins 7&9 shorted:
• All four status lights come on briefly, then go out.
• Three yellow lights come on after a few seconds (no green light).
• The green light comes on and remains on, and all yellow lights are off.
It seems not to have gone through the diagnostic test. If it had, only the two middle yellow lights (toner low and paper out) lights would have been on during the test.
If indeed the diagnostic test was run, it would seem to be reporting SIMM #1 failure. Is the SIMM referred to the RAM or the ROM?

I don’t have a service manual, but I found the print test micro-switch. I engaged it while powering-up the printer. It seems to have no effect. The printer status lights quickly display as for the regular power-up as reported above.

The fuser is good. I measure 2 ohms and 284,000 ohms at the indicated places.

Thinking perhaps the replacement toner cartridge was defective, I re-installed the old one. No luck – same symptoms. The replacement cartridge made more noise than normal and I wonder whether it damaged the engine in some way.

I’m at a loss what I can check next. I would sure like to get this printer functioning again. It is old, but has had only light use at home.
Weird lights are usually indicative of a formatter failure. What you need to do is to open the back door and cheat the door interlock. Looking from the back, you'll see a piece of plastic extending from the door on the right. It pushes on a piece of black plastic on the printer, which through a linkage blocks and unblocks an optical sensor on top of the printer. What I do is fold up some paper and wedge it in the opening to hold the plastic piece in the door closed position. Do not push too hard or you'll jam the works up above. You'll know when you have it actuated as the printer will fire up. Now you can watch the action. The fuser should light up for about 30 seconds. If it just comes on briefly and the motor runs briefly, that would be a motor problem. If it lights up the full 30 seconds, then it should go to warmup and at that point, the only thing that could be bad is the formatter. After it warms up, you should be able to initiate an engine test. You stick a paper clip in the hole as shown in this photo of an HP4 (same engine) It should print a lined test page.
by moe on Dec 5, 2007 at 9:23pm Add comment
You can get the service manual here:

by unknown on Dec 6, 2007 at 8:54am Add comment
Thanks for the tips so far. I forgot to mention that I had already tried overriding the door interlock and saw no fuser light up on power-up.
This entire sequence from power-up to stable status lights takes only 12 seconds.
Sounding like a motor problem? That would be consistent with the failure just after installation of the rebuilt toner cartridge.
Since I am presently in Europe with no service/repair resources, how can I obtain and install a motor? Is the motor dependent on line voltage? And is there some way I can verify whether the motor is bad? I didn't notice much on the motor in the service manual that I downloaded, but I will check again.
by nyc1956 on Dec 6, 2007 at 3:44pm Add comment
The ones that I have observed with a motor problem, the motor did run for several seconds. I've never seen a totally dead motor. I still think the fuser should light up until the DC controller detects an improper motor rotational speed. The motor is tested early in the initialization process. New ones are no longer available and I've exhausted all the used motors that we harvested from parts printers. In any case, I don't think it's a motor problem. Laserwriters are hard to diagnose. I kind of doubt the service manual would be of much use. I'm kind of leaning toward a DC controller problem, but that's just a guess.
by moe on Dec 6, 2007 at 5:58pm Add comment
Where the Apple service manual could help is that it contains diagnostic flowcharts that step through the startup sequence, with instructions on what to check for a variety of symptoms. Just thought it might be worth looking at.
- unknown