Samsung ML-1450 printer not working properly

Question

I purchased a Samsun ML-1450 laser printer about a year and a half ago and it's been great ... until earlier this year I went to use it and the print quality had declined, like it needed a head clean. I ran the Dr Printer software that came with the printer, but still it couldn't find/troubleshoot the problem.I've taken the toner cartridge in and out and it seems fairly heavy/full so I don't think it needs replacing but I'm not sure.The cartridges are expensive so I don't want to have to buy one if it's not necessary. Can anyone help ?thankyou