Broken Floppy Disk Drive or Power Supply? Old Mark II repair

Kevin Busse Apr 01, 2024

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This is a good test to use to determine whether the issue is a failed FDD (Floppy Disk Drive) or Power Supply on a Mark II Yamaha Disklavier.

There are only 5 steps required to know if the Floppy Disk Drive or Power Supply has failed on a Yamaha Mark II Disklavier.

1. Power off

Start with the control box powered OFF.

2. Access Maintenance Mode

Push and hold both "Song Select" buttons [|<<] and [>>|] while powering the unit on to access "Maintenance Mode."

3. Confirm Display readings

Push the [R] button one time. You should see "01" on the numerical readout and "Test Play" on the LCD screen.

4. Push Play

Push the [Play] button.

The piano should begin playing a chromatic scale starting at the lowest note on the piano and moving upwards.

5. End Test

Push the [Stop] button at any time to end this test.

You can then power the Disklavier off.

How to determine whether the Yamaha Mark II Player Piano failed due to the FDD (Floppy Disk Drive) or Power Supply?

If the keys did not move, then the power supply has likely failed.

The reason for this is because the test that is being performed does not require a functioning Floppy Disk Drive. Although, it requires a properly functioning Power Supply.

Possible Solutions for repairing a Yamaha Mark II Player Piano

I've replaced the old floppy drives, which requires opening the control box and reinserting a ribbon cable to the new FDD from an existing circuit board.

I've also replaced Power Supplies, where it's always recommended to ship the power supply unit for repair to Tap Electronics in Buena Park, California.

I owe credit to Noah Jolly who helped create these simple instructions for determining the root cause of this issue.

His website is Ground Grown Circuits where he performs professional repair for a wide variety of analog and digital audio equipment.