I have to warn you this fix is not for the faint of heart!
My Hp 3330 laserjet has been pushing paper for me for almost 20 years, without problems aside from every once in awhile changing the toner cartridge.
About a week ago it would sit there making funny noises a the display stated Scanner Warmup. So I unplugged the printer and plugged it back in with the same results. Since this is my only B&W printer I had two choices 1) Buy a new printer (can't afford it), 2) use my Bother Color printer but the Black cartridge was dead! 3) fix the damn thing (hey I can fix jet engines!) So what the hell! When I Googled the problem, I got several hits (videos), and they explained that you don't need to buy anything. It is only the mirrors (in the black thing by the lamp) and they are most likely dirty. So you have to take the whole top apart. Control Panel and shroud, both side covers, and the upper side shrouds as well. This is like a bazillion screws so you will need a good mag tip Phillips screwdriver.
Then Q-tips to clean the mirror frames (5), I cleaned them with Windex. But the glass deck was another story, hot water, and Dawn.
When everything was cleaned I put the glass deck in place and plugged it in. Eureka, it bitched about not having any paper in the tray!! I then unplugged it for the last time and screwed it all back together. It is back where it belongs, on the stand, pushing Paper!!
Here is the video I used as a guide. Sorry, the guide was pulled on YouTube. So here is the blow by blow but no video you have to follow the pretty pictures!