Pale prints from LaserJet 1320

[AeneSE]

Around ten years ago I got a, then,  fairly new Laserjet 1320tn. It has been working well with duplex, despite it being a bit big for home use and a small issue with driver for Windows 10.

But lately the printouts have become really pale. Prints look OK, but black is now light grey - grey. I've tried to replace the toner and reset the printer. But at the moment it's still more grey than black despit setting Density = 5, Economode = Off and Resolution = ProRes 1200.

Is there something I can do or is it more economical to look for a new laserjet?

[Valsimot]

Press and hold the green button for a few seconds on the printer panel to print a demo page scan it and post it here so it's visible. Depending on the environment a laser optics can be dirty that resulting in very light print quality.

If you have replaced toner and reset printer laser is the next possible source of the problem. 

[AeneSE]

Thanks. Don't have a scanner at hand, but tried to take a photo of it.

[Valsimot]

It could be a dirty laser ( optics and mirror). 

Under top cover after 2:45 in video https://www.youtube.com/watch?v=hK1NeaoKrwE  if you want to open laser and clean it with cotton swab.