Meat Plow wrote:
On Tue, 21 Jul 2009 17:37:46 +1000, Bob Larter
wrote:

notme wrote:
What is it about laser printers that causes UPS manufacturers to recommend
they not be powered by a "stepped approximation to sine" UPS? It's a SMSP,
isn't it? What makes it special such that it needs sine-only? No such caution
re. computers, etc...
The big difference is that lasers usually have a mains powered quartz
lamp inside the fuser assembly to cook the toner onto the paper. My
guess would be that the lamp puts a huge current spike on the mains each
time it powers up, which is every minute or so. If so, that spike might
overload the UPS.

The fuser in the older HP lasers was on even waiting for a print job.
There was a thermostat on the lamp strip inside the roller to keep the
fuser roller at a constant temp.

Yes, that's correct. (Fixed hundreds of them, back in the days.)

The warnings on UPS date back to
those times.


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