Model Yamaha ME-50 no power

Power Supply issue. Dealer service.

MOX6 / MOX8 Owner's Manual - Yamaha

https://usa.yamaha.com > mox6mox8_en_om_b0
PDF
Utilize power outlets that are on different branch (circuit breaker or fuse) circuits or install AC line filter/s. In the case of radio or TV interference, ...
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https://www.google.com/search?q=Yamaha+MOX+6%2C+no+power

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Models differ, but when we had a similar issue, replacing the power cord did the trick. We almost didn't check it because the lights were coming on; there must have been enough power to light the lights but not play the sound ! hope that helps!

first - check the power supply if it's really giving power.
Get voltmeter or plug it to something else you know it's working.

If you are sure it does and still nothing, you need to check the fuse inside the P80. I've been there, it's not so hard to open it
(from below of course)

BTW, it's advisable to user surge protector on such delicate devices like computers and keyboards if there are any fuses that have blown. I can't tell you how many times a blown fuse has stopped equipment from working. I had a blown fuse go in a microwave oven a few years back. I called a repair guy while on a job to fix my Leslie (many years ago) and the culprit, a blown fuse. I could have fied it myself if I had given it more thought.

Check the internal fuses first and you might save some money and a trip to a repair center. , sometimes a fuse can look good even when it is blown. If you have a voltage tester do a continuity check on the fuse just to be certain.It's possible that the P80 does not use internal fuses especially since it uses an external 12 volt power pack There might be info on the fuse in the P80 manual. Otherwise try Yamaha support. A lot of low volage gear run of AC adaptors is unfused.

Another possibility is that the power connector or switch on the P80 is broken. DC power jacks are liable to get broken solder joints due to movement, especially if they are circuit board mounted and not chassis mounted. If you know what you are doing test the connector and switch with a multimeter.

If they are good then also check the wires from the switch to the main board. They a probably connected with a plug, which itself can come lose.

You can test for bad connections with the power off. Only test with the power on if you really do know what you are doing! You won't electrocute yourself but you can easily damage the keyboard if you are not careful.

Unless you are experienced in electronics repair that is as far as you should go.

if no indication of power, change fuse by opening the back cover....if its showing power consult a qualified tech.

fuse

Check the output of the power supply itself.

Ac plug wires
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Most keyboards have fuses, and this could be the problem. If there is access to a fuse on the back panel, check to see if it is still good. If there is no fuse cap, then the internal power supply may have a blown fuse. If so, it's time to see a service tech...

That varies depending on the model of the keyboard.

Download the user manual and look in the "Specifications"... You will find the power consumption listed there. Most will be UNDER 50 Watts.

An answer, but likely not a solution. I believe all Yamaha PSR series keyboards use the same 12 VDC adaptor, so I looked at the electrical schematic for another model I have. There seems to be no fuse on the power input. There are two components shown on the positive and negative wires off the power socket, but the symbols do not look like anything I have seen for fuses - they may be resistors. Power goes directly to a 5 VDC voltage regulator, which powers all of the solid state componenents. Too much voltage of the wrong type could have easily ruined many of the sensitive components.

Your only hope is to check the power socket area for the possibility of having fuses. My drawing shows the power socket, voltage regulator, and audio power amplifier being on one circuit board. That may not actually be the way it is in your model.

Good luck!
(your English is fine)