Unbrick Yamaha A4000 and A5000 Samplers

A5000 receiving a firmware update via MIDI

The A4000 and A5000 are the last hardware samplers produced by Yamaha in 1999. They're pretty sturdy but it's not impossible to brick them, specially when messing around with their IDE and SCSI internals, or accidentally shorting things. This can lead to a corrupted OS and unbootable sampler. There is however a completely undocumented feature that allows to flash the OS via MIDI/SysEx, thanks to booting into a small software that's in a ROM somewhere and that will start listen to whatever arrives on the MIDI IN-A port.

This info, and the SysEx version of the firmware, is not even in the rather extensive service manual. My guess is that its existence eventually leaked into the community from people working in Yamaha service centers and who realized that many returned bricked/b0rked A4000/A5000 could be revived like this, and it was simpler to give the info as a first try, as opposed to go through a full RMA. At time of writing, there is only one private forum that mentions this trick, and only one site left that has a copy of the MIDI files needed. I'm putting it all here, to duplicate this specific and scarce info.

The overall process is done in two steps because only an old firmware exists as MIDI file: so 1. we update to 1.07 via MIDI, and 2. we update to latest 1.50 via floppy.

All the files needed are in the File:Axk-firmwares.tar.xz archive.

Update to 1.07 via MIDI

• Plug the MIDI out of your soundcard into the MIDI IN-A of the sampler
• Enter the FIRMWARE VERSION UP MODE by turning on the sampler while holding the three buttons COMMAND/EXIT, ASSIGNABLE and AUDITION
• On your computer, playback the main.mid file

aplaymidi --port 20 main.mid  # you can find the right port with aconnect -l

• When no more PACKETS are received and the line check sum is displayed, then the update is finished.
• If you have an A4000, you can reboot, no need to do anything else. Unbricked!
• If you have an A5000, you need to update the secondary CPU firmware, reboot into the FIRMWARE VERSION UP MODE, and playback the sub.mid file

aplaymidi --port 20 sub.mid

• When no more PACKETS are received and the line check sum is displayed, then the update is finish. Your A5000 can be rebooted. Unbricked!

Update to 1.50 via floppies

• If you have an A4000 you need one floppy, if you have an A5000 you need two.
• Format them with an MS-DOS filesystem and copy the following files:
  • A4000: 0475mst1.pgm
  • A5000: 0475mst1.pgm and 0475slv1.pgm
• Insert the floppy with 0475mst1.pgm in the sampler
• Press DISK, then COMMAND/EXIT
• Select LOAD_OS and press 4>GO
• Select OS FileType Main, the sampler will scan the floppy drive and if it finds the right file it will display (OS file version:V1.50)
• Press 5>EXEC&CONT and follow the instructions, the process is over when all the function key LEDs are on.
• If you have an A4000, you can reboot, no need to do anything else. All done!
• If you have an A5000, you need to follow the same steps again with the floppy containing 0475slv1.pgm, and this time selecting OS FileType Sub. Once everything is flashed, you can reboot, no need to do anything else. All done!