I picked this unit up a while back.
The problem is somewhere on the main board - it won't boot.
I tested the PS and ROM in my recently sold PX7 and they are working fine.
So snag this if you want to keep some spare parts around.
The power supplies are hard to get and the composer ROM is a useful addition to the MP/XL/PX units.
$150 + shipping/paypal CONUS only
send an email and I'll send you a link to pics.
peace,
john