Akai MPD226 Service Manual page 22

In this test, the ADT1 Manufacturing Test application will send messages to the MPD226 to
set all the segments on the LCD display first on and then off.
For both the "on" and "off" tests, the Tester should examine the LCD and use the indicated
buttons to confirm whether the subtest has passed.
– Test Passed: press the control indicated by "PASS" bubble message.
– Test Failed: press the control indicated by "FAIL" bubble message.