I ordered toner from Ink Owl to refill my Yellow cartridge in my Brother MFC- L3770cdw. It's not a starter cartridge that came with the printer, it's a compatible toner cartridge I ordered and used up already. I go thru a ton of these compatible toner cartridges as I print more than your typical 5-10% laydown. Thus the attempt at replacing the toner only. The procedure I received from Ink Owl involved purchasing a 5/8" hole melting soldering iron to melt a hole in a particular area of the ink cartridge to remove, empty, clean and then add the new toner. My issue is that there's already a white plug in the side of this cartridge that appears to allow access to the same area that the hole would. I verified this by sacrificing one of my many spent cartridges. I drilled a hole in the area where they wanted me to melt a hole, pulled the plug on the side, stuck a long wire in the plug hole and watched as it appeared in the drilled hole. It's the same chamber! So, after vacuuming out all the toner, (a lot of toner), and thoroughly cleaning the rollers, I filled the cartridge with the yellow toner and put the plug back in the side. Looked great and didn't have to purchase or disassemble anything. Upon installation back into the printer, the MFP L3770 still wanted yellow toner. I reset the yellow STD cartridge multiple times using the correct procedure. Still wanted toner. I know that the plugged hole on the side and the area where I drilled a hole, both go to the chamber that holds the toner to be metered and dispensed onto the developer roller to make yellow appear on my prints when needed. And I believe there are no sensors in the cartridge to monitor the toner level. I think it just goes by number of prints. What am I missing?