asked Nov 4, 2001 at 6:38am
Apple Apple StyleWriter II

(Un?)usual Laserwriter IIg issue

I bought a used LW IIg. It came with a filthy fuser & defective fan. After cleaning the fuser, I was able to print. I left it on for about 6 hours, after printing about 6 pages. After turning it on the next day, the fuser kept on heating until one of the two sensors popped. Since the printer was not able to heat up any more - it went out of order.. I then bought a LaserJet II (which worked fine!!) for parts, swapped the complete fuser-unit (+ the upper fan)- and it popped again..

The voltage I've measured on the power-supply's plug for the fuser is constantly 230V - even after that accident., from the moment you switch the printer on..

I have a LaserJet III now, which works fine - and I want to swap basically the complete Canon SX engine, so the only parts remaining would be the Apple mainboard,the case and the *DC board*.

However, since the DC-board interfaces to one of the two sensors in the fuser, I'm afraid that it could be the source of the problem - and I would have swapped >90\% of the printer for nothing...

So my questions would be - could this overheating be caused by the DC-board ?

Are the two sensors thermal-one's ?

And the one in line with the heating wire just for protection (i.e."popping") or is it supposed to regulate the 220V (Europe) down counter-proportionally to the temperature (->thermistor)?

Or is the power-supply supposed to shut-off the voltage (steered through the DC-board or similar)?
I wanted to swap the stuff this sunday, so any advice greatly appreciated, before the third printer goes south - for nothing .. :(
The problem you experienced is caused by the ac power module. That's the module that the power cord plugs into. Unfortunately, the fuser usually suffers permanent damage when it overheats. The nomex cleaning wand melts, the lamp burns out and the thermal fuse (the round metal one) blows. The other smaller sensor is a temperature sensor. I've seen fusers where the plastic end bushings melted and the upper and lower rollers fused together.
by moe on Nov 4, 2001 at 9:38am Add comment
Ok, thanks Moe,
I've already fixed that by browsing through some earlier posts here.
I'm just wondering if I should change all the parts in the LW with one of my LaserJets (II). I am a bit worried about swapping the big switching power-supply, since the LW-one is newer (rev.4 '90 vs. rev-1 87), the LJ's parts are cleaner & less used though (as new..).

Thanks for your hints.
by unknown on Nov 5, 2001 at 2:40am Add comment
The older power supplies had board problems. Areas of the board would get hot and the solder connections would break. Other than that, all the parts on top are the same. The lower boards aren't interchangeable.
by moe on Nov 5, 2001 at 9:57am Add comment