- Press Menu then Mono.
- Press Up four times. You should now be in maintenance mode.
- Press 8 0 then press Mono many times until you see "Purge: XXXXX". "XXXXX" should be showing a number.
- Press 2 7 8 3 to reset the purge counter to 00000.
- Press Exit then press 9 9 to exit maintenance mode.
These steps are based on instructions from this blog.