Purpose of a Drum unit in laser printer?

I have a Dell 1700n laser printer. The printer worked amazingly until we ran out of toner, I ordered a replacement toner cartridge and it worked well for a while, now with yet another new toner cartridge, the print quality is getting lighter and lighter and less distinct. I saw something about a Drum and am aware of the piece in question, but I don’t understand its purpose? Can someone give me some insight into a laser printers drum:

http://cgi.ebay.com/DRUM-for-DELL-310-5404-1700-1700N-P1700-1710-1710N_W0QQitemZ270459551748QQcmdZViewItemQQptZBI_Toner?hash=item3ef8a54004

I also am not sure if this is what I need or not, I don’t want to invest more money if it’s not what I need here. Thanks for help.

The drum is there to actually hold the electrostatic charge to transfer the toner (ink) to the paper. here’s something you can look at too http://en.wikipedia.org/wiki/Laser_printer

So if the drum is what holds the charge to put the toner particles on the paper, it would stand to reason that a very used drum would have difficulty printing in the best resolution yes?

[QUOTE=If-Then;2448048]So if the drum is what holds the charge to put the toner particles on the paper, it would stand to reason that a very used drum would have difficulty printing in the best resolution yes?[/QUOTE]

More then likely yes

Is there any way you can check the page counter on the printer? Most printers keep a count of the number of pages since the printer was first used or the counter was last reset.

The imaging drum for your printer has a rated life of 30,000 pages, so after going through a few toner cartridges, you could well be approaching the usable life of the drum. The reason I suggest looking for a counter is that even if a toner cartridge is rated for 5,000 pages (which I think yours are), the yield can be a lot more than this if you print a lot of pages with only a small amount of print. For example, if let’s say you were getting an average of 8,000 pages from each cartridge, you’ll hit the 30,000 page mark before your 4th toner cartridge has finished.

Finally, check if your printer has any “Toner Save” type feature. If so, try turning it off to see how the print compares. For example, many Samsung printers have this to reduce toner usage when the feature is enabled, but it results in faded print, which will become more obvious as the drum ages.

I’ll have to look into the page counter, and toner save options.