My MOX refuses to turn on :(
The MOX usually extremely quick to boot up. However, of late, I noticed that sometimes it takes a while to turn on. I turn on the power button, but the keyboard does not respond. I keep it on for a while and then after a few minutes, the screen and panel buttons light up. This delay time slowly increased and now it completely refuses to turn on.
I live in a very humid region and this problem has started during the monsoon season. Has anyone faced a similar issue? Any ideas with what could be going on?
I have tried to warm up the circuit board using a hair dryer, but that did not help. My PSRs970 keyboard is kept in the same room, but did does not have this issue.

Have you checked with a known-good power adapter?

Yes I checked it with a known good power adapter yesterday. It did not turn on.

Today I kept the switch on for a long time..and it came on after about an hour! This is with my own power adapter. Also, I verified using a multimeter that my power adapter is outputting 12v.

Your member profile doesn’t indicate your location. However, your post mentions the arrival of monsoon season. Certain electronic parts tend to have short lives where temperatures are elevated. If your MOX has been in a particularly warm environment for several years, there may be a connection.

Although there can be other causes, problems such as you’ve described are often due to failing electrolytic capacitors. Unfortunately, proper service procedure typically requires more than a multimeter. This thread (concerning the repair of an S90 )…
http://www.motifator.com/index.php/forum/viewthread/478647/
...shows why the service manual and an oscilloscope might be needed to pin down some problems.

I am from India, on the west coast. It’s been a particularly wet and long monsoon season. Average temperatures are around 30 Degrees Celsius. The temperature has not changed much, but humidity is very high during the monsoon season. I am going to get it serviced tomorrow. Hope they can figure out whats wrong. Fingers crossed. Will update their findings here.

The engineer told me that there is a problem with the power supply board. He could not figure out what the issue is. He tried connecting a different board from another MOX and my keyboard turned on, so he recommended that I replace the power supply board.
This board (Part# WV188500) is not available with Yamaha India and needs to be ordered from the factory. I have placed the order, but they say that the waiting period is 30 to 40 days. It’s gonna be a long wait!

I finally got my hands on the power supply board yesterday. I opened up the MOX and swapped the old board with the new one myself and voila, the MOX is back to life :)… back to playing music and programming patches now!