Hi,
that's what I've found, but haven't had the chance to test it:
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This is the procedure to reset PG40. Worked for MP180.
1) Power off the printer. While holding STOP/RESET button, power on the printer.
2) While holding POWER button, release STOP/RESET...
I like this model for it's cheap laser toner cartridges (especially compatibles). Never don't have any experience refilling them myself though.
I mainly print cd/dvd covers and I'm happy with CLP-300N.