She placed the disc on middle C. The key depressed silently. On the screen, a voltage reading climbed: 0.00v ... 0.87v ... 1.42v. It settled at 1.50v. She pressed ENTER.
But the service manual warned of ghosts. On page 89, a small, ominous note in the "After Repair Calibration" section: Note: The M50’s operating system stores calibration data for the keybed’s aftertouch sensor in volatile memory. If main power is disconnected for more than 72 hours, the sensor’s baseline drifts. A manual re-calibration is required. Failure to do so results in aftertouch triggering at 100% pressure at all times, effectively ruining the expressive capability of the instrument.
She plugged in the power supply. No smoke. Good.
The service manual was open to page 47. "After replacing the KLM-3056 Main Board," it read, in its flat, Japanese-to-English prose, "perform the 'Full Reset of Global Parameters' followed by the 'Rotary Encoder Initialization.'"
But tonight, only the Korg M50 was singing again.