Korg M1 stuck on “Init Prog” — need repair advice

Synth Repair
,
1

Hello! I’m trying to repair an original Korg M1 (61-key).

Symptoms:

  • On startup, the display shows KORG Music Workstation M1 #25, then Init Prog.

  • The INT and PROG indicators remain lit.

  • The keyboard produces a piano sound, but the factory programs (such as Universe) are missing.

  • The internal battery has been replaced.

  • Changes to program parameters can be saved and retained after power-off.

  • I tried reloading the official factory preload file m1preld.syx using MIDI-OX and Bome SendSX, but the display and programs did not change.

  • I also tried requesting program dumps over SysEx, but currently receive no MIDI input data when attempting a dump from the M1.

I have checked the global MIDI channel, EXCL is enabled, and Memory Protect is OFF.

My question: What hardware or memory-related faults could cause this behavior? Is there a reliable way to determine whether the problem is with the main board, program memory, or MIDI interface before replacing components?

I would appreciate advice from anyone experienced in repairing the original Korg M1. Thank you!