HL LJ 2300 smears company logo on left side of form

So you've replaced the transfer roll and fuser with no change in the defect.

The first thing to look for when troubleshooting these kinds of defects is to see if the defect is present on the imaging drum (which is integrated into the toner cart on most newer monochrome laser printers).  This might be a little tricky to determine, especially if your defect is only on one part of the page, but the process is simple.  You need to start the print job and then stop it right after the laser writes the image to the imaging drum and it rotates to the point where you can see the image.  This will naturally take you a few tries to get it to stop at the right point.  This is called a half-test, by the way, because you're stopping the imaging process halfway through.  Note that you will definitely cause a paper jam while doing this, so just be careful when you pull the paper back out.  And you will have loose toner on the page as it hasn't gone through the fuser yet.

With 70% of the parts involved in the imaging process integrated into the toner cartridge, you can see how a lot of problems turn out to be caused by a defective cartridge.  I know you said it seems to happen only when you run out of toner, but then I understand that it happens all the time now whether you use a new cartridge or not.

The most important question here is:  Are you using genuine HP toner?

>>if the imaging drum is inside the cartridge then why would the problem still occur when using a new cartridge?

We're not concerned with the drum itself; we're concerned about what happens to the drum.  This is why I asked you to do the half test to see if the problem was being caused by something besides the toner cart.  The imaging drum is like a blank slate that you write to - it doesn't do any image formation on its own.

I had to ask if you were using genuine HP carts because it's pointless to continue troubleshooting if you are not.

>>where does the laser actually reside in one of these printers, is it possible the laser assembly is the problem?

The laser scanner is usually at the top of the printer because it has to sit right up against the toner cart.  When you install a toner cart, it pushes the laser/scanner shutter up so that the laser can get to the drum.  (It has a shutter on it in the unlikely event that you decide to work on the printer while power is applied and somehow the beam bounces off your bling and hits your eyes.  Even with the shutter on, you should never wear jewelry while servicing a laser printer.)  The laser hits the imaging drum in the toner cart which gets your image on the drum, where it's then transferred onto the paper through an electrostatic transfer process.

If the defect is on the drum after doing the half-test, then you can look at the laser scanner and/or the high voltage power supply.  The HVPS supplies the large amounts of voltage needed for the transfer process.

There are two parts to the laser printing process, at least in HP printers - everything up to and including the transfer process, and everything after.

>>If so can it be taken apart, cleaned &/or fixed?

It can be taken apart but I don't recommend doing this as you might get dirt/dust inside of it, which will ruin the scanning mirror - the sound of the scanning mirror spinning at ungodly speeds is that spooling-up sound you hear when the printer starts printing.  You can, however, clean the mirror which sits behind the shutter.  It is unlikely that this is the problem unless you use this printer in a dirty environment but it's worth a shot.  If this part fails, which is indicated by a laser/scanner failure error, it's very easy to replace; usually a few screws and a couple ribbon cables/harnesses.  But in your case it obviously hasn't failed completely.

>>i wish the manual on these printers included total maintenance instructions on how to take them apart.

If they did, I would be out of a job :-)

I hope we are getting somewhere with this problem and I'm not just confusing you more.  I would definitely try to do the half-test and check the drum for the image defect.  It might be easier to see on the drum if you can reproduce the part of the image that has the defect and make it fit all over one single sheet of paper, then send it to the printer.  Again, to check the drum, stop the printing process as soon as the leading edge of the paper gets to the transfer roller.  When you pull out the toner cartridge and look underneath the shutter, you'll see your latent image with the electrostatically attracted toner stuck to it.  The drum is usually a pale turquoise or shiny green color.

If you’re getting smears or traces (ghost image) your fuser might be the problem.
These new printer have a Teflon type fuser with an element to fuse the toner to the paper. I have needed to replace the fuser a few times to get a good remanufactured one. Don’t be fooled because you changed it. The brown Teflon ‘Sleeve’ on the fuser doesn’t turn or slips and it smears the toner while fusing it. If it wasn’t a Genuine HP kit the chances are higher this is the problem. You will also find it does this more when cold.

The scanner mirror can be a problem with density. If it’s in a dusty environment it can accumulate dust and depending where the dust settles you will have light areas on your print. Clean the mirror with the green or blue brush if this model has one. Or you can open the scanner assembly and clean the mirrors with a Q tip. Make sure your comfortable with tearing up your printer. It’s a job for an advanced user.

Here’s a place you can get a service manual. Search for your model.
http://www.eserviceinfo.com