K5 Repair Issues

I'm new to this group, so I would like to say hello to everyone out there!  I purchased a 
used K5, without a working backlight, a few months ago.  I was forced to program with a 
flashlight.  I finally got to a point where I decided to replace the backlight myself.  I 
ordered a backlight from one place, and decided to purchase the last version of ROMs 
available from Kawai, as the keyboard was using v1.0.

The problem started after I installed the new backlight.  After soldering the two 
connections, I reinstalled all the PCBs, and turned on my K5, eager to see the "new" 
display.  Nothing happened.  I didn't even get any sound!

The connections I made were clean.  I might have left the iron on the board a tad long, but 
could overheating a part on the display board cause the entire keyboard to stop function?  
I double checked to see if I may have created a short, but everything looked fine, and the 
fuses still looked good.  I did notice what appeared to be rust on the connections to a 
raised white box located on the right side of the instrument.  When closed, it would have 
been located near the PSU.  Is this the inverter?

I would love to get this instrument running again.  If anybody could give me any sort of 
advice, I would greatly appreciate it.  I was really starting to enjoy this instrument, and it 
would be a shame if it ended up being scrapped for parts.  Thanks in advance.

Ivan