Check to see if the image of the printout to be, is on the image drum. If it is there and isn't being transfered to the paper then something like the high voltage corona wire or hight voltage supply isn't charging the paper.
(From: FAXFIXR (firstname.lastname@example.org).)
There are two corona wires, the charge corona and the transfer corona. The charge corona is the one you should look at. It is located in the toner cartridge so the easiest way to check is try another cartridge, even one that is out (or almost) of toner. If you don't have another, then you can check yours. If you look at the cartridge in it's operating position, there is a black mylar plastic film that covers a slit on top from end to end. The mylar covers the corona wire but allows you to insert the little green tool, found inside the copier, to wipe the corona. If the tool is there, stick the pad into the slot and wipe it back and forth. If you hear a slight screeching sound (like a violin) then the corona is there. If it's not there, then the cartridge must be replaced.
(From: Tony Duell (email@example.com).)
(The following was written for HP LaserJet III but it is generally applicable to other laser printers and photocopiers.)
For starters, try a new toner cartridge. I've found these can cause all sorts of problems...
Now, blank pages are due to one or more of :
Start it printing a test page (the 'engine test' switch on the DC controller is useful for this). When the paper is still going through the printer, turn it off, open the lid and pull back the cover over the drum in the cartridge. Is there a 'latent image' on the drum? If so, check the EHT power supply and transfer corona assemblies.
Check that you plugged the cables into the scanner properly. They don't always make good contact. This will normally cause a 'beam detect' problem - I forget what the error is for that (51? 52?). It's possible that there's an O/C in the cable, of course.
If you have an IR detector (of the type used for testing remote controls), unplug the optical fibre from the DC controller and point the end at the IR detector. Again print a test page. If the laser and scanner are working, you'll get some IR (laser light, so take care) out of the end of the fibre.
There is a mechanical shutter in front of the laser in the scanner that's opened by a lever under the scanner when the cover is closed with a toner cartridge in place. The idea is to prevent any laser light getting out if the printer is run with the cover open/no cartridge. Is this working correctly. Did you get the scanner correctly on top of it.