I love my Yamaha P-250 stage piano but

I lost a power supply on it last year ( It would not boot) So I found one online and installed and it worked but took MUCH longer to boot. Now, I came in to hear a horrible noise coming from my 250. huge noise that DOES go down if I turn down the MASTER VOLUME. So currently the keyboard is completely useless. I am willing to troubleshoot and replace parts etc… But finding pars is a problem. A main board and another Power Supply would be a good place to swap out. I will read the other threads here. Thanks in advance gang! ::grinning:

Another Syntaur member was nice enough to give me a P-250 earlier this year with a dead power supply. I am still invested in fixing it but have had almost zero time to look at it. I bought the manual from Yamaha but it doesn’t have schematics in it. I’m curious where you got your replacement power supply, and whether you have found schematics?

I haven’t reverse engineered this power supply yet, and I’m not sure I’m up to that task although I’m going to try, but from working on other audio boards, I know that problems on the power supply can definitely create noise. I’ve worked on arcade boards which have requirements for -5v for example, only for the audio section, and without that -5v source being stable it had a terrible buzz.

I’m hoping that if I can find schematics, or even basic definitions of what voltages should be coming out of each connector, I may be able to fix these power supplies, which might be good for both of us.

Do you have access to proper schematics? The doc I got from Yamaha seems only to have pictures of the circuit board unpopulated.


Hi Steve,
The Yamaha P-250 Service manual CD-R SM P250(I bought from Yamaha Support) is what you need.
I thought I could attach a pic? But I guess I cant? Maybe private message? ( Ah I see I need Basic Privileges’ to PM or post pix) I’m too new. Ha!
*BTW, that power supply, the MA-60 is also used on other Yamaha keyboards. It also contains the Power Amp for the built-in speakers.
I’m actually going to borrow my friend’s P250 to swap out suspected boards.
The schematics in the Yamaha Service manual are excellent! I color-printed some up on ledger-size paper. But a 32" monitor is even better. I really don’t want to get a CP-300 as I like feel and the sound of this keyboard better.
Take care, Jay

P-250 has a very simple PSU except that some of them use bad caps that tend to leak and destroy the circuit board (got one here right now - not a p-250 but very similar)

Just to make sure it is just a PSU noise issue - remove CN500 from the AJK board (the one with all the jack connectors on it) - the on the AJK board CN500 add a 10k resistor from Pin 9 (no mote) to Pin 5 (+12V) to fake the mute relay then power on - if still noisy all digital stuff is OK and the problem is almost 100% on the PSU !!


… and this is all that is to the PSU

Hi Wernersaurus,
Thanks for getting back!!!
I now have 2 P250s in my garage studio on 2 tables. I have yet to dissect the patients.
I’ll try and upload the Block Diagram. You will see that the volume knob affects the level of the noise
MV2 off of the AJK Board. So I believe the “noise” is coming from "before" the MA60 Power Supply/Amp Board.P250%20BLOCK%20Diagram

Yes you are correct - I completely mis-read your initial sentence - reading it goes way with the volume down - my bad!.

On that note - that leaves only the DAC and the main CPU before that.

Did you try a full factory reset - just in case the memory got corrupted during your PSU issue ?

to enter the Test Program
While pressing the [C#2], [F2] and [G#2] keys, turn on the [POWER] switch.

Go to Test 040:Factory Set using the Up/Down arrows of the Tempo section the use MIDI OUT button to execute.

When this test is performed, the factory preset data will be set in the Flash ROMs when the power is turned on the
next time. “Factory Set OK” is displayed on the LCD display. It takes about 15 seconds.

When done Power Off/On

One thing I always noticed was that if you went through LOTs of different sounds and instruments and played them, when you came back to the grand, it was no longer “true”. A reboot always solved that problem but although memory is cheap these days, back in the day, they wanted to save on memory both ROM and RAM! But this basic keyboard is still much better than a lot of the “new” keyboards. And it just feels better! Combined with the FC3A sustain pedal I can really make the strings weave in and out. I want to try if I get this friggin thing fixed to try 2 P250s one left hand and one right and listen how completely isolated L&R actually records. I need to get home and start tearing things apart! Ha!

Well I tried pressing the [C#2], [F2] and [G#2] keys, turned on the [POWER] switch and it does not go into a Test program on either P250. What am I missing? And after a long boot, the piano plays fine for about 10 minutes then crackles and the crackles worse.

Make sure you select the correct because the first 3 notes on the left ar A0, A#0 and B0

I was an octave low as I started with A1 being the 1st key. Thanks!
However, I get into the
040:Factory Set
Factory Set –
and it never says OK nor does in place an * asterisk in front of the display item.
Now it Finally says OK after 15 minutes or more
Time to swap some circuit boards?
Say…Where are you getting this reset info from? because;
I have the:
Service Manual, SM P250 CD 2018-ish
The Owners Manual, 2002 V960150, and the
Data List 2002

I am a YAMAHA Certified Service Tech and Service Center ( CASIO, KAWAI, KORG, ROLAND and KURZWEIL as well). I thought the service manual had that in it - under the heading “TEST PROGRAM”. Then again - it is divided into two parts P250_SM and P250_SM_C (circuit diagrams). I suspect you may only have the latter?

Run the first 7 as well - may give an idea what is going on.

OK Thanks Wernersaurus!
Well I’m probably going backwards now.
Got 040:Factory Set OK
Rebooted. It kept loading, loading, loading for 45 minutes.
But strangely, the piano played fine while this reset loading was going on. But it never stopped loading.
So i (big mistake), powered down then up.
Now the “Please Wait” message is permanent, it does not boot at all and even in “Test Program” it will not take Tempo up/down commands.
Question. Is there a foreign site (I’m in the US) that may stock a DM processor board for the P250?

Hmmmmmm …

  • P-250 (2003, GH action) is 18 years old now. Yamaha only guarantee parts for 10 years after that is all pure luck. AND - should they have one it’ll be in the $600 … $700 range.

P-250 is not the most sought after instrument - this may be your best bet:

Yamaha Keyboards and MIDI Parts, Audio, Video and Lighting Accessories | Full Compass Systems

I pulled the DM Main board out of the good P250 and put it including 2 attached Wave ROM boards into the bad one. There was a slow (1 minute) boot-up but it worked fine.
Then I put in the original Wave ROM boards and tested 1 at a time. They worked! so the ROM boards are cool but the DM board is sick. It will not go past the “Test Mode” or “Waiting” state.
At the C7 file erase does not work at all. Hmm…