12/640 Why does it become hot after more than 20 pages ?

The imaging process uses very Voltages to generate high electrostatic charges to develop the image on the drum. This can generate ozone, which has a distinctive smell. There is typically a carbon filter than captures some of the ozone, but after many years it is likely to be used up. Since this printer is out of production, new ozone filters may be hard to find.

The fuser roller heats to about 440 degrees Fahrenheit to melt (or "fuse") the plastic toner particles into the surface of the paper.

The printer is getting hot because it is doing its job. It smells funny because of that heat plus ozone.

In addition to a jam that produces a crumpled sheet inside the printer, printers can sometimes suffer from what I call a mis-pick. That is, the paper never makes it out of the input tray. This error will be cleared by cycling the power on the printer, because there is no sheet stuck inside.

This can happen because the paper is too slippery or not slippery enough, because the humidity is wrong, because there is too much or too little paper in the tray, because the paper was not fanned before being placed in the tray, or is not quite in the best position in the tray, or because the pick-up roller is getting a shiny, glazed surface on it.

If this seems to be the case, check and fan the paper in the tray. Take a look at the pickup roller. If the roller is glazed, scrubbing it with an eraser can break up the glazing a little. For tough cases, rubber rejuvenator should be applied. If you cannot locate rubber rejuvenator, "Goof-Off" latex paint remover does a fair job.