HP 1320n prints faint

[ChronosHD]

I got an old 1320 which prints faint letters, and I try to revive it. I tried cleaning the laser module, but was clean. I tried to replace the cartridge with an original one, the first page was 100% black, but the second was the same faint.

Can someone propose next steps for troubleshooting?

Edit: I´ve printed the config pages, the most importand details I see:
- Total printed pages: 16934
- Economode: off
- Print density: 3
- Black print cartridge: 100%