"My owner's manual never mentions developer anywhere. This copier uses toner cartridges which mount above the dispenser and drop toner into a mechanism which distributes it to the drum. There is a white plastic bottle which catches excess toner and eventually fills up and needs replacing. They say to replace the bottle, but I just empty it, wipe it off and reinstall it. Only the toner cartridge and the bottle are mentioned in the useless owner's manual."
(Responses farom: Nate Morrison (firstname.lastname@example.org).)
Well, that's all they think you need to know. They want you to call the dealer if the copies are crappy.
The reason you should just toss the used toner bottle is the dust--it is messy and not good for your respiratory tract.
Some copiers use developer; others don't. How long it lasts before it runs out is basically in how the copier is engineered. Some gets carried away every time you make a copy. Pretty soon there isn't enough to carry toner to the drum anymore.
"So, if my copier needs developer, how do I obtain it? Where does it go? I suspect that I purchase a bottle of these 'iron particles' and dump it into the slot where the toner drops into, but I don't want to do ANYTHING until I know the right thing to do."
If you need developer, you can get a kit from the local service shop. You'll pay plenty, to be sure, but not as much as if someone came out and did it for you. It might not be a bad idea to invest in a service manual - I got one for our Minolta for around $20.
"Why is this rather simple maintenance procedure kept a secret from the owner? Is Mita trying to make money for their authorized repair outlets?"
Well, that's another of those reasons they want you to hire the serviceperson at a ludicrous rate. (the local place gets $99/hour!) You have it pegged.
Another reason is that they want to promote the idea that _their_ copier is service-free. Telling any prospective buyer that in 50,000 copies it will require professional service is NOT a selling point. :-) The copier is designed so you can change toner and paper and that's it. Anything else is always "see your authorized dealer" in the useless owner's manual.