"whit3rd" wrote in message
...
On Jul 19, 11:21 am, 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

The main heater (the one that fuses the toner so it sticks to the
paper) is usually run on a thermostat, using a big SCR (triac, to
be more specific). Those SCRs can trigger on fast-rising spikes
on the power line, by capacitive coupling from cathode to gate,
so steps in the power-in voltage are contraindicated.

So a heater of that sort takes its power directly from the line?