I have changed the toner on my dell 1720 it's still not printing well do i have to change my drum

First of all dirty rollers are not the cause of your problem as long as the printer is picking up the paper.
Black marks or streaks on a DELL 1700 series printer are usually caused by the drum assembly which, in this model, is separate from the toner cartridge. There is no repair, you need to replace the drum assembly and perform the drum reset procedure. In very rare cases a buildup of residual toner on the fuser can cause marks as well, but I have never seen this on a DELL printer.
To replace the drum:
1. After removing the paper tray, open the front of the printer.
2. Remove the toner cartridge by pushing down on the black release tab and pulling the toner up and out of the printer.
3. Pull the drum assembly straight out of the printer using the blue plastic handle.
4. Carefully unpack the new assembly and install in the printer. Be careful not to touch the photo-sensitive roller underneath.
5. Reinstall the toner cartridge, close the printer and insert the paper tray.
6. Perform the drum reset procedure exactly as follows:

power off and open front door hold down the continue button as you power on printer leaving front door open when error light comes on release continue and close front door. toner low, load paper, ready, and continue will all be lit. press cancel slowly 4 times or until just toner low lights up. each time you press cancel, the light sequence should change when just toner low is lit, press and hold continue button until lights cycle up and down in sequence. release continue.. toner low will be lit again turn printer off, wait 10 secs or so and then back on press continue button to print off settings page and check under cartridge information, photoconductor value is 0K (zero)

Remove the toner and the paper tray and open every door on the printer. Take a can of air and blow out every nook and cranny in the printer. Check and carefully wipe all rollers. There a fuser kit in the printer, likely in the back. If you feel comfortable with it, remove the fuser kit and use a can of air to continue cleaning. Reassemble the printer and run a few test pages, it may look like a bigger mess for the first few pages (up to 25). However, as you run the pages the print should clear up. If you still have a streaks on the pages, you will likely need to order an maintenance kit from dell. This kit should include the fuse, rollers and other replacement parts for the printer.

I hope this has helped you

it can either be the imagine drum or the toner. If there are scratches or smudges on the imaging drum it can cause that problem, or if toner is escaping out of the toner cartridge. try removing both, I believe they come out in one piece and inspect.

This is usually due to a dirty imaging drum roller (green roller below toner). Remove the toner / drum assembly, then separate the two. Now slowly rotate the imaging drum roller by hand using the gear on the side of the cartridge (Try not to not touch the drum roller with your hand, as oils from your skin may cause further problems + toner is nasty) Look for toner splotches to the left and right on the drum roller as you turn it. If you see any you can clean them off with a damp paper towel. Then reassemble the printer and hold the continue button down until you hear the printer start then release it; this will print a test page.. Hopefully that will take care of the issue. Also while you got the assembly out of the printer you can clean the glass print-head lens using a clean, dry, and lint free cloth. The print head lense is located within the recessed area in the top of the printer.

- I have seen that happen to a bunch of those printers and that is usually all it is. Let me know if that takes care of it.

Picture of Drum + Print Head lense for a (1720 / 1720DN).
Link to Dell manual about drum & print head.

(Full link below)

(http://www.support.dell.com/support/edocs/systems/prn1720/en/1720_en/en/d0e4183.html#replacing-the-imaging-drum)

Hello

You have to check couple things in this case.

Ensure that the printer cover is closed.

1. Remove the toner cartridge.
   
2. Firmly shake it side-to-side and front-to-back several times to redistribute the toner.
   
3. Reinsert the toner cartridge, and continue printing.
   

Repeat this procedure multiple times until the print remains faded. When the print remains faded, replace the toner cartridge.

or
The imaging drum is approaching full and needs to be replaced. Order a new imaging drum.

The corona wire is not charging the drum properly. Try pulling the toner cartridge out and then re-seating it. If this doesn't work, try a new toner cartridge as the corona wire is usually included in the cartridge.

If you are using a refill toner, there's an outside chance that the supplier put toner with the wrong electric charge in the cartridge. Again, changing the cartridge should fix this(assuming the replacement is from another batch).

The transfer roller may have toner on it that is making that mess. Remove the toner and drum, look inside the printer, there is a grey roller towards the back of the printer. Is there toner on the right hand side that corresponds to the print out? If there is, cleaning it may only make it worse. Replacing it would be the best solution. You would want to make sure that the drum is clean after replacing the roller, if it is not ,then it will transfer to this roller once again.

I believe this message is occur because the laser printer drum needs to be replaced, not the toner cartridge.

These are two different things. The part is a DELL 310-8710 Drum Unit. Just google DELL 1720N drum and you should be able to find one.

There could just be a lot of toner inside the printer, but it could also be the drum unit (which also collects the waste toner) is so full that it is leaking.

This typically happens when the 'replace drum' indication is reset without actually replacing the drum.

If you have reset this without replacing the drum, and the print count is in excess of 30,000, you probably just need to replace the drm unit.

The second link was the helpful information. Also, to cut through all of that --

If you need to reset the counter:

1. Remove drum kit with toner

2. Make sure all print jobs are flushed otherwise whatever has been sent and not printed will come spewing out.

3. Hold down CANCEL Button until all lights flash through.

4. Slide the drum kit and toner properly into the Printer.

done.