Adding toner to a Samsung ML-1720 is it hard ? or better to buy a new cartridge Thanks?

Yes it is hard.


For one they have a fuse on the cartridge that ';blows'; when the cartridge is empty preventing it from printing further. That needs to be replaced.





The printer itself has a drum unit attached (which arranges the image) that is designed for single use and needs to be cleaned.





Thirdly there are nylon gears and electrostatic rollers in a toner cartridge that need to be check and sometimes lubricated in order to yield optimal results.





Finally toner, should not be inhaled. The black toner dust is carcinogenic and should only be handled with extreme care including a fine particulate mask, gloves in a well ventilated area, preferably under a hood.