Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Problems with Yamaha MX100B with Disklavier

We purchased a used Yamaha MX-100B (with Disklavier) last year and had it professionally moved and tuned once it arrived. It has worked fine since then, up until about 1 week ago. Part way through a playing a disk, the piano went silent and displayed "Piano Power Off - (PWM Over)!" If you power down and restart, it will again play partway through a song and display the same error. I'm curious if there is a simple fix for this or is it something to call out a pro for? I'm an electrical engineer with a heck of a background in "fixing" things, but without a maintenance manual or finding anything in the operations manual, I don't know where to begin. Any thoughts?

ftp://tech:disklavier@216.154.248.26/ Try this link, (copy & paste) look under service manuals. Hope this helps.

Many thanks. Found the error message and as I suspected, looks like it is going to be a power supply related issue. I always like to know the problem before I call in someone else - don't like not knowing what I'm asking someone else to do. Thanks again - I appreciate the link and the manuals.

Richard I have the same problem with my Disklavier MX100 II it will give me the same message Piano Power Off - (PWM Over)!" and will do the same if you restart it play one or 2 songs and stop did you ever fix the problem with yours thanks in advance Marge

@Rich H: I have a limited experience with these instruments, but at least the one we host is exposed to similar problems - albeit randomly, but still. If you cure the problem by switching/repairing the power supply, please let me know.

Hello I had the same problem and have solve it:

The power supply have a 20V-regulater (IC2 MJN78M20FA) witch is operated outside of its specification. At the entrance he receives 50V instead of the 40V allowed! Therefore, it switches off automatically.I put a strong Zener diode in series, so that it works with <40V.
Problem solved!

Check to see if the pedal solenoids are overheating. There should be pedal adjustment instructions on the inside cabinet. Sometimes the power error will be related and if the solenoid is too hot then it will terminate power to the system long enough for it to cool down to operating temps then you can prompt playback until it overheats again. Two cents.

Hi everyone.
I know it's been a couple of years since this post, but I now have a similar problem.
I have an MX101R, which seems to be the Japanese domestic version of the MX100B.
Was working perfectly and then all of a sudden, it wasn't. Wouldn't even play from a floppy!
Sometimes it will start to play a MIDI file through Cakewalk, but then it gives up after only a few bars!
All the diagnostic tests 1-9 are OK except #7 the MIDI one, which has NG, even though the MIDI cable is connected. And the notes test #8 only plays up to note #30. (LCD says Get data = 55)
Re the MIDI test #7, you can't activate the MIDI switch with the red light wheh you start the test programme, because the + and - keys held together prevents you from doing that. And when the test in running, pressing the MIDI switch does nothing.
Any clues anyone? Is this related to the 40/50v problem above? How would I know if this is the case?
I don't get the "PWM over" error message though.
Ian Griggs
Sydney Australia

The frustrating thing with the Service Manual is that it doesn't tell you how to address any of the NG faults!

Has anyone had any luck with finding a replacement power supply for their Yamaha Disklavier piano? My MX100II power supply failed with several of the electrolytic capacitors leaking fluid and damaging the board. The unit is not viably repairable and Yamaha advised there is no replacement power supply available. It would be a shame to render this instrument, which I paid over $15,000 for, only partially useful.

I am hopeful that some combination of off-the-shelf power supplies and some custom circuitry could replace this.

Since a fine piano should be a viable instrument for many decades, I am disappointed that Yamaha has decided to drop support for this piano.

I have power unit for Disklavier .（WC769209）
I'v confirmed that operation.
If you are interested, please sent me a private message.

https://goo.gl/photos/8QtExRhvqvZ5Y7bo9
https://goo.gl/photos/LReTaQ2K4TzxM1p99
https://goo.gl/photos/enXkCyqiooq1X7Pn9

I sent an email with photos of my power supply and details of parts I replaced. I'm looking forward to your reply.

Hi, I'm new to this group. I have the same MX100II upright piano. Basically, it'd play for 2-3 mins and stop with a few fading notes. If I turn off the piano and turn it back on. The same would happen. Is it easy to diagnose and fix it myself? I am not an electrical engineer, but I do have the service manual. Thanks in advance for your response!

Thank you for contacting us. I have not noticed it because no mail has arrived.

How to check Disklavier power supply.
Cb1=AC power input.
Cb6=10switch+ 9switch- 8 pon- 7 pon-
Cb5=5/6/7 high voltage

Power supply startup routine.
Ac input -power
switch 10+9 connect.
Relay 1 on.
System power +8v and +20v goes to
Disklavier check thermo and protec.
Disklavier ctrl board send back pon.
pon+ goes to Low.
Relay 2 on .
High voltage out put.

At what point does the voltage not come out?

@Pro-TAC
Hello, I´m ctive Austria / Europe. My MX100II PowerSupply failed with a defect XK413A0 PowerStream module (capacitors already replaced). Here in Austria I would be charged about EUR 500 (US$ 700) with a new XK413A0 - only the module!, so I´m replacing the defect power supply with 8V, 20V and 100V power supplies.

Do you have any suggestions where to buy a XK413A0 for better pricing or can you even give a hint how much amperes the 8V , 20V and 100V power supply should have ?

Would be good to get these info´s before replacing the power supply.
regards
ano1

>ano1

I'm tired of repairing the power supply.

When I bought a power IC from AliExpress but it was a fake,superbad.
And there is currently no way to get it. Please ask to TAP in California.

If there is a voltage on the secondary side of T2, the IC is normal.
Most of the causes are the leakage of the capacitor and the pattern and land are often melted.

Since 8v is a system power supply, I guess it is 1-1.5A. Since 20v is an LED power supply it is about 2A, and 110vDC is a solenoid power supply, so I guess it is about 5A.
But please take own risk.

Thanks for your help and info.

Because of max power stated on license plate of 150 Watts, I tried with a dual supply AC/DC with 20V and 8V 5A and and DC/DC StepUp converter to 100V (which is sourced from AC/DC supply 20V and could make 10A when delivered from AC/DC power supply
I found the fuses on 8V is 1.6A, and 100V is 4A, so this should be maximum ratings...
I wanted the original power supply still in use (seondary side) so I injected the external power supplys on secondary side of original power supply. I had to raise 8V to approx 9V (until voltage on power connector read correct 8V) and 20V I raised to approx. 30V (more power to DC/DC converter). On power on the AC/DC is too weak (cant deliver startup amps), but after 2 bumps power on 8V and 20V is there and stable, but 100V will not be activated , because the POE+ dont get low...
So I found more problems on my disklavier (perhaps lightning- overvoltage defect...).
The controller shows some Japanese letters, DISK can be read without problems and controller tries to play, but with no 100V nothing happens....
Do you have any hint for change Japanese to English ?
In test mode L and R and PowerOn , some tests are fine, but some are also not (MIDI NG! and PIANO IO TEST NG!)...

Perhaps you have any suggestions....
regards
Herbert

>ano 1
I was mistaken for a unit for Japanese version.
I don't guess other people are interested in this topic, so please contact me directly.