Just bought a used Yamaha ES8 and poof!!!! any gurus gimme some wisdom here???

[docpain]

I bought this used ES8 from some kats in greenville,ws for 1200$ +70S/H [and it had a MLan installed]
they told me its been there prolly couple months but works fine and would be shipped very well packed...
it was descent packed (used high density foamboard) double boxed with thick corner supports.
soon as i plug it up in 30 seconds it goes dead... i bang on it and it boots back up. start playing dead again...
it seems the only way it would stay powered up was if you barely touch the keys to play. finally i hit a key to hard n poof
its dead for good now . I decided to break into it n find out if i could track down a short. 1st thing I notice all the screws were just started so somebody wasnt being honest at some point
It appears to Key assembly is isolated
and that gave me the idea that possibly the keys actually work off of ground instead of + for sensors ) anyways I removed key assembly, removed sensor circuitboards
remove silicone sensor buttons (cleaned and silicone preserved the silicone pads there were no wire filimants or broken contact points that could short out the keys) .
Now im left seriously contemplating buying the actual sensor for 30$ before taking to a certified tech [which in knows prolly gonna cost me 250$ just for goin thru the door then 20% markup on parts
and hourly rate as well for diagnostics]. Does anyone know of a similar situation happening before or could shed more light on the subject for me? Does it sound like a logical risk to just buy the sensor and try? --- i.e im disabled /live on a minimal amount & was hoping to start recording using said ES8 vs me actually playin all the instruments 1 by one to record and have all that mess in the livingroom.
im down 1300 already on this guy no matter what --- I just wana know if its worth it // has anyone else had this happen/ any techs around that could shed some light or have insight with what info ive presented? know how to test the key sensor? (i.e. have mutlimeter but no scope..). thanx for any help!

[mjbphotos]

If you bought it through Ebay, you've got buyer protection. Ever hear about a 'deal too good to be true'? You paid less than half of what a working keyboard would cost ...