I just installed a new NOS toner cartridge in a 20 year old HP 4050n. The big caveat with those is that the old cartridges have long been out of production and

I just installed a new NOS toner cartridge in a 20 year old HP 4050n. The big caveat with those is that the old cartridges have long been out of production and the dried up rubber seals on them crumble into bits after removing the OE sealing strip. You need to fill in the opening to prevent toner from vibrating out into the machine.