Hi, I´m Eric, and I´m posting a question about my Yamaha Motif ES rackmount synth. Until a couple of weeks ago, it worked great. Then, one day, I turned it on, and nothing happened–the LED screen didn´t even light up. Thinking the most obvious answer was a faulty AC power supply, I ordered a replacement. Unfortunately, that didn´t solve the problem. Anyone have any useful advice/suggestions?
Thanks,
Eric Shank
Are any other lights coming on at all on the machine when you power it on? If there are lights other than the LCD screen and just the LCD is blank and not lit up then it’s just the display that needs to get replaced. It’s a simple repair to replace the display. If no lights whatsoever are coming on at all. I would disconnect the power cord, remove it from the rear of the rack module. Open the module’s case up and check for any fuse that may be blown. A fuse is a mini clear component with a silver cap on each side. If you do see a fuse and it looks grey and smokey on it’s inside that indicates it’s burnt out and you need to replace it with the same type and specifications fuse.When the machine is opened look to make sure there are no leaking components around near it’s power supply and the internal jumper cables are firmly connected. Also make sure that there are no dark blackish marks on it’s green pc board. If you’re going to check out the inside of the machine please wear rubber gloves like dish washing rubber gloves. This way you don’t give any of the modules chips or components a static discharge. Good luck. I hope this helps. 
P.S. I’ve been there myself and it feels very frustrating. Stay positive, it can be repaired by a professional if you can’t figure it out.