The first thing to check is the power supply, with a voltmeter, as you wiggle the cable at the power supply end and at the keyboard connector end, to ensure that it is providing a rock steady output of the correct voltage. Then, connect the power supply to the keyboard and power it up. As it is going through those "reboots", wiggle the power supply connector, where it plugs into the keyboard, to see if the situation gets better or worse. If it does, you probably have a bad power supply connector or a bad power socket in the keyboard. I am going to discount a bad microchip (integrated circuit), because when they go bad, they stay bad until replaced. A bad chip problem does not come and go, unless it is heat related, but then the problem does not appear until the unit has had time to heat up and will not go away until the unit cools down. This does not appear to fit your symptoms. One other item to check without having to open the keyboard's case is the buttons. Make sure you do not have any buttons that have body oil and dirt collected between them and where they pass through the front panel, causing them to stick down. OK ! Now, we need a tech to go back inside the case. One possibility is a bad electrolytic filter capacitor. Usually, these act the same as a bad microchip - when they go bad, they stay bad, and the unit does not work at all, until the bad component is replaced, but sometimes, as they are going bad, they will momentarily short out, and in the case of computer type (keyboard) circuits, cause a reboot. The momentary shorts can occur anywhere from every few seconds, to every few minutes, to every few hours. Bad electrolytics will usually show signs of physical stress - swelling, splitting open, spilling the electrolyte out onto the circuit board or surrounding components, and discoloration of the capacitor and surrounding circuit board from overheating. BUT . . . NOW . . . we get to the one I am betting on. The PSR-3000 has 20 circuit boards beside that main circuit board that Yamaha replaced. Some of them plug directly into the main circuit board, while the rest are connected by ribbon cables - and that is where I am placing my money. A bad connection on one of the plug-in boards would most likely have been cleared when Yamaha unplugged it from the old main board and reseated it onto the new main board. Everything you have described and the video you posted just screams "intermittent connection" of some type. Ribbon cables are the bane of aging electronic circuits that use them. For all the other "quality" components that might surround them, ribbon cable connectors, by design, come under the category of "cheap junk" - not where the cable's plastic connector fastens onto the circuit board, but where the plastic connector is crimped onto the ribbon cable itself. Those things are just a failure waiting to happen. I have no idea where to tell you to begin looking. My thought, if I really wanted to keep my PSR-3000, would be to just replace them all. My only other "guess" would be a bad video display loading down the power circuits and causing reboots. The MOTL PSR's with the color displays are noted for this, but the PSR-S900's were the worst and those symptoms don't really fit what you are seeing. You might want to also post your question in the PSR-3000 section of the psrtutorial.com forum. Many of the folks over there "cut their teeth" on the PSR-3000, and some are still using theirs - at home and for gigging.
